The shooting of a woman at an Owings Mills apartment complex was the precursor for the ambush killing of two New York City police officers later in the day, law enforcement officials said. 
 
 Police in New York and Baltimore County said they believe Ismaaiyl Abdulah Brinsley shot and wounded his ex-girlfriend before 6 a.m. Saturday at an apartment near the Owings Mills Mall, then posted anti-law enforcement messages on social media as he traveled to Brooklyn, N.Y. 
 
 There, he approached a marked police vehicle parked in the Bedford-Stuyvesant neighborhood around 2:45 p.m. He "took a shooting stance" and fired a handgun several times through the window, New York Police Commissioner William Bratton said at a news conference. 
 
 Officers Wenjian Liu and Rafael Ramos were struck in the head, and taken to a hospital, where they were pronounced dead. Police said Brinsley, 28, ran into a subway station, where he shot himself in the head. 
 
 "Today, two of New York's finest were shot and killed with no warning, no provocation," Bratton said. "They were, quite simply, assassinated — targeted for their uniform." 
 
 Elise Armacost, a Baltimore County Police spokeswoman, said officers tracking Brinsley's posts and the location of his cellphone notified the NYPD's 70th precinct of the threats against officers in a phone call at 2:10 p.m. 
 
 Handout Instagram post geotagged to Brooklyn Instagram post geotagged to Brooklyn (Handout) 
 
 Bratton told reporters that the warnings were received just as the officers were shot. 
 
 "The tragedy here is that just as the warning was coming in, the murder was occurring," Bratton said. 
 
 The shooting comes at a time of heightened tensions amid grand jury decisions in the police-involved deaths of Michael Brown in Ferguson, Mo., and Eric Garner in New York, among other incidents. Bratton said police were investigating Brinsley's background to see what role his anti-police messages played in the shooting. 
 
 In New York, police were reacting by instructing officers not to take enforcement action "unless absolutely necessary," the New York Times reported. A memo circulated by the police officers union also said at least two units were to respond to all calls, "no matter the condition or severity." 
 
 New York Mayor Bill de Blasio urged the public to come forward and report possible attacks against law enforcement. "When a police officer is murdered, it tears at the very foundation of our society — it is an attack on all of us," he said at the news conference with Bratton.. 
 
 The killings follow the shooting six days earlier in Baltimore of Officer Andrew Groman, who was shot in the stomach while asking a man to get out of a vehicle during a traffic stop in West Baltimore. 
 
 That incident sparked concern from the Baltimore police union that officers were battling anxiety that could compromise officer safety. The suspect's attorney, meanwhile, raised the idea that the attention around police brutality had spurred "survival instincts" to kick in for the 19-year-old, who has a prior conviction for a gun offense. 
 
 On Friday, the Baltimore FBI office issued a memo that the Black Guerrilla Family gang was targeting "white cops" in Maryland, an agency spokeswoman confirmed. The memo, circulating among officers, said a contact who had given reliable information in the past said members of the gang — connected to the high-profile corruption scandal at the Baltimore City Detention Center — were planning to target white officers to "send a message." 
 
 A federal law enforcement official said Brinsley had no known ties to the BGF. 
 
 Baltimore Mayor Stephanie Rawlings-Blake said Saturday in response to the New York officer killings that "the overwhelming majority of law enforcement are good, decent and honorable men and women who care deeply about the communities they serve." 
 
 "It is an act of cowardice to target law enforcement in such a shameful way, and doing so does nothing to honor the lives lost in police custody," Rawlings-Blake said. 
 
 The Baltimore County shooting occurred inside an apartment in the Greenwich Place complex in the 10000 block of Mill Run Circle. Police had said earlier in the day that the woman was shot in the abdomen by a male whom she knew and that they were searching for a suspect, whom they did not identify. 
 
 The apartment complex lines the parking lot of the Owings Mills Mall and is next to a movie theater. Residents and guests must pass through a gate in order to enter by vehicle, though it is accessible by foot. 
 
 The management of the apartment complex tucked a letter into the doors of residents saying the shooting was the result of a "domestic dispute." 
 
 "We share this information with you to assure you this was a private, isolated incident," the letter read. 
 
 The woman, who was not identified by county police, was listed in serious condition but expected to survive, county police late Saturday. 
 
 Within hours of the shooting of the officers in Brooklyn, reports began surfacing that the incidents were linked. 
 
 Armacost, the county police spokeswoman, said detectives learned of the Brinsley's threats against police on the photo sharing site Instagram at about 1:30 p.m. and began trying to determine his location. They tracked his phone and determined he was in New York's 70th precinct, and officers from Baltimore County and New York discussed the posts in a telephone call, she said. 
 
 County police said they faxed a warning poster around the same time, and at 2:50 p.m. a Teletype was sent to the NYPD's real-time crime center, a data warehouse. 
 
 Bratton said the messages posted to Instagram were "very anti-police" and showed a "very strong bias against police officers." 
 
 "Whether that was the principal motivation, we'll try to put together what was the actual motivation," Bratton said. 
 
 On an Instagram account taken down Saturday afternoon, an image of a silver handgun was accompanied by the message, "I'm Putting Wings On Pigs Today. They Take 1 Of Ours…..Let's Take 2 of Theirs #ShootThePolice #RIPErivGardner #RIPMikeBrown This May Be My Final Post." 
 
 Posts on the account were geo-tagged to Georgia and the area around the Owings Mills Mall. The posting with the image of the gun was tagged in Brooklyn. 
 
 Brinsley appeared to reside in Georgia, Bratton said. Online records from Georgia's Fulton County sheriff's office show that Brinsley has been arrested nine times since 2004 including charges of simple battery, criminal trespassing, carrying a concealed weapon, obstruction of a law enforcement officer and shoplifting. 
 
 His last arrest in the Atlanta area came in April 2010 when he was charged with possession of marijuana, simple battery and terrorist threats. He was convicted of disorderly conduct and shoplifting, while dispositions of the other cases were not clear. ||||| Two NYPD officers were shot and killed at about 2:45 p.m. on Dec. 20, 2014. View Full Caption 
 
 BEDFORD-STUYVESANT — Two police officers were killed in an "ambush" as they sat in a police vehicle Saturday afternoon by a gunman who bragged on Instagram about plans to kill police, Police Commissioner Bill Bratton said. 
 
 "Today two of New York's Finest were shot and killed with no warning," Bratton said. 
 
 Mayor Bill de Blasio and Bratton described their deaths as an "assassination." 
 
 After the shooting, gunman Ismaaiyl Brinsley, 28, then entered the nearby Myrtle-Willoughby G train subway station where he fatally shot himself, Bratton said. 
 
 Early Saturday morning, Brinsley shot his ex-girlfriend in Maryland, Bratton said. A warning from Baltimore-area police was faxed to the NYPD, but arrived too late. 
 
 NYPD Forms Honor Guard to Salute Slain Officers View Full Caption DNAinfo/Katie Honan 
 
 "The tragedy here is just that the warning was coming in the murder was occurring," Bratton said. 
 
 Officers Wenjian Liu, 32, and Rafael Ramos, 40, were sitting in a Critical Response Vehicle having taken part in a patrol exercise in 79th Precinct and were parked near Myrtle and Tompkins avenues at about 2:45 p.m. when Brinsley walked up and shot them both at close range, Bratton said. 
 
 Brinsley approached from the passenger side, where Liu was sitting, with Ramos in the driver's seat, took a shooting stance, and fired through the passenger window, striking both officers in the head, Bratton said. 
 
 "They may never have actually seen their assailant, their murderer," Bratton said. 
 
 Liu and Ramos both worked in the 84th Precinct, and were taken to Woodhull Medical Center, according to the NYPD, but were later pronounced dead. 
 
 "Our city is in mourning. Our hearts are heavy," de Blasio said. "We lost two good men who devoted their lives to protecting all of us." 
 
 Brinsley was taken to Brooklyn Hospital. 
 
 At 5:45 a.m. Saturday, Brinsley shot and wounded his ex-girlfriend in Baltimore County, MD, Bratton said. 
 
 Brinsley then posted threats against the police on both his and his ex-girlfriend's Instagram accounts, sources said. 
 
 He said he was going to "put wings on pigs today," in a post that earned at least 140 likes. 
 
 He also used hashtags referencing the deaths of Eric Garner and Michael Brown, who were both killed by police. 
 
 "They take 1 of ours," the post continued. "Let's take 2 of theirs." 
 
 The woman's mother notified Baltimore authorities that she saw the social media rants, police said. 
 
 Baltimore police then sent a fax that arrived as the officers were being ambushed, Bratton said. 
 
 More than a hundred emotional police officers lined the street as the two men's bodies were taken from Woodhull Medical Center just after 9:30 p.m. 
 
 Afterwards, the head of the city's largest police union blamed de Blasio and recent anti-NYPD protests for the shooting. 
 
 "There's blood on many hands tonight," Patrolmen's Benevolent Association President Pat Lynch said. "That blood on the hands starts on the steps of City Hall, in the office of the mayor." 
 
 Rev. Al Sharpton said in a statement that he had spoken to the Garner family and that they were "outraged" the gunman had invoked the Staten Island man's name. 
 
 "Any use of the names of Eric Garner and Michael Brown, in connection with any violence or killing of police, is reprehensible and against the pursuit of justice in both cases," Sharpton said. 
 
 Baltimore County police said on Facebook that Brinsley is the suspect in the shooting of a woman in Owings Mills, MD. 
 
 They tracked him to New York City by his cell phone, sources said. Brinsley may have had a connection to East Flatbush, Bratton said. 
 
 Ramos and Liu were part of a special program to increase police presence in Police Service Area 3, which patrols nearby public housing complexes, said City Councilman Robert Cornegy, who represents the area. 
 
 "They were just a presence, they weren't over-policing," he said. "They were here as a presence to make the community feel safer." 
 
 Officer Liu, who had been on the force seven years, was married just two months ago, Bratton said. 
 
 Officer Ramos, who was also married and had a 13-year-old son, had been on the force for nearly three years, Bratton said, adding that he had been a school safety agent from 2009-2012. 
 
 Cassandra Harrell, 52, lives nearby and said she was "hoping and praying" that the shooting had nothing to do with the recent decision not to indict a police officer in the death of Eric Garner. 
 
 "I'm very worried there's going to be a backlash because of this horrible crime committed against the police," she said. 
 
 "This sets us back 1000 percent. I don't even know how you come back from this," Cornegy said. "If you wanted to articulate what the worst case scenario could be at a time when the city is trying to get back on track with police and community relations, this is it."
– As New York City grapples with the fallout from the execution-style murders of two NYPD officers, Police Commissioner Bill Bratton yesterday lamented that "two of New York's Finest were shot and killed with no warning." Except, as he amended, "the warning was coming." What went down, via reporting in the Baltimore Sun and DNAinfo: Police in Baltimore County say that shortly before 6am yesterday, 28-year-old shooter Ismaaiyl Brinsley shot and wounded an ex-girlfriend at an apartment complex outside Baltimore. She is listed in serious condition, but expected to survive. Police believe he then traveled to New York City, posting threats on social media along the way. Brinsley posted to Instagram: "I'm putting wings on pigs today. They take 1 of ours, let's take 2 of theirs. This May Be My Final Post. I'm Putting Pigs In A Blanket." He used hashtags Shootthepolice, RIPErivGardner (sic), and RIPMikeBrown. According to the Sun's screenshot, the post garnered at least 221 likes. A Baltimore County Police spokeswoman said officers became aware of Brinsley's posts about 1:30pm, and began monitoring them, as well as his location via his cellphone. They tracked him to NYPD's 70th Precinct, which they called at 2:10pm to warn of the threat. They sent a Teletype at 2:50pm. But it was too late: Officers Wenjian Liu, 32, and Rafael Ramos, 40, were shot at 2:45pm.