Question: Which English convicted drug-dealer killed two persons in a gun and grenade ambush?

Context paragraphs:
SS Emidio: SS "Emidio" was a 6912-ton tanker of the General Petroleum Corporation (later Mobil Oil), which became the first casualty of the Imperial Japanese Navy's submarine force action on California's Pacific Coast.  It was one of four attacks on shipping, the others being "Samoa, Larry Doheny," and "Montebello", all attacked off the coast of California before Christmas.  "Emidio" was sailing in ballast from Seattle, Washington en route to San Pedro, California.  The Japanese submarine I-17 found "Emidio" off Cape Mendocino on the early afternoon of 20 December 1941, immediately attacking with its 14-cm deck gun.  Realizing that the situation was futile, Captain Farrow raised a white flag and gave the order to abandon ship.  Ignoring the surrender, the I-17 continued firing from its deck gun, blasting three crew members who were lowering a lifeboat overboard.  Four crew members remained on board: a radio operator and three engineers.  When the I-17 fired a torpedo, it struck the engine room and killed two of the engineers and injured the third.  In total the I-17 hit the tanker with five shells from its 14-cm deck gun and one torpedo killing five crew members.  A Catalina flying boat of 44 Patrol Squadron attacked I-17 with depth charges, but the submarine dove and escaped.  The Coast Guard Cutter "Shawnee" rescued the remaining 31 survivors who had rowed 16 hours to Humboldt Bay.  The abandoned tanker drifted north and broke up on the rocks off Crescent City.  The bow drifted into the harbor, where it lay until scrapped in 1959.  The remains of the hull are still in the harbor, near a commemorative plaque.  The site has been declared a California Historical Landmark #497.

Dale Cregan: Dale Christopher Cregan (born 6 June 1983) is an English convicted drug-dealer and murderer who was sentenced to a whole life order in prison for four counts of murder (including the killing of two police officers) and three separate counts of attempted murder, meaning that he will never be released from prison.

20 March 2012 Iraq attacks: The 20 March 2012 Iraq attacks were the sixth simultaneous wave of bombings to hit Iraq during the insurgency and the second such major assault since the US withdrawal at the end of 2011.  At least 50 people were killed and around 250 wounded in highly coordinated attacks spread out in at least 10 cities.  The deadliest attack of the day took place in Karbala where twin bombings left 13 dead and 50 injured.  In the northern city of Kirkuk a car parked in the parking lot of a local security office exploded, killing 13 and leaving almost 60 wounded.  Several explosions rocked the capital Baghdad, including mortar attacks close to the Green Zone and a suicide blast near an intelligence building opposite the Foreign Ministry – three people were killed and nine wounded in that attack.  Numerous other bombings and shootings took place all across the country, including Fallujah, Samarra, Baiji, Hillah, Latifiya, Tuz Khormato and others.  A car bomb in Ramadi killed two and injured 11, as unidentified gunmen shot and killed two police officers in a nearby village.  Authorities in Baqubah discovered and successfully disarmed at least eight explosive devices.

Rail push trolley: A Rail push trolley or simply a push-trolley is a hand-pushed trolley used to inspect the rails and other track-side railway infrastructure.  It is a simple trolley, pushed by two or four persons (called trolleymen), with hand brakes to stop the trolley.  When the trolley slows down, two trolleymen jump off the trolley, and push it till it picks up speed.  Then they jump into the trolley again, and the cycle continues.  The trolleymen take turns in pushing the trolley so that the speed is maintained and two persons do not get tired.  Four persons are also required to safely lift the trolley off the rail tracks when a train approaches.

Murders of Nicola Hughes and Fiona Bone: On 18 September 2012, Police Constables Nicola Hughes and Fiona Bone, two Greater Manchester Police officers, were killed by Dale Cregan in a gun and grenade ambush while responding to a report of a burglary in Greater Manchester, England.

Canal Area, San Rafael, California: Most of San Rafael's low-income residents live in the Canal Area, along with many affluent residents.  There is at least one concern (on Harbor Way) that rents slips for boats that people can live aboard legally.  The more affluent residents live in the houses constructed in the 1960s right on the Canal and in two housing developments in the eastern part of the Canal's residential area: Baypoint Lagoons (constructed in the late 1990s) and Spinnaker Point (constructed earlier).  Some real-estate agents refer to these two developments as being in "East San Rafael", to avoid the stigma of the name "Canal Area".  The low-income homes (almost all of which are apartments) are inhabited mainly by immigrants (documented and undocumented), from a variety of countries.  Seventy percent are Hispanic, 11 percent Asian, 10 percent Caucasian, 5 percent African-American and 4 percent are of other ethnic groups.  This area provides a location for workers who hold low-income jobs that are essential to the functioning of the community to live close to their place of employment.  Although the majority of residents in this area are low-income workers, most of the apartments in which they live are neither subsidized nor less expensive than comparable apartments elsewhere in San Rafael.  In order to pay the relatively high rents, the residents resort to sharing their dwellings with many roommates, typically at least two persons per bedroom, plus one person in the living room.  Often as many as eight or more persons, including children, will occupy a two-bedroom apartment.

Surinder Singh (Ashok Chakra): Subedar Surinder Singh was an Indian military officer with the 3rd Battalion of the Sikh Regiment.  On 3 March 2002, he single-handedly killed four terrorists near the Line of Control in the Rajouri sector of Jammu and Kashmir.  Singh killed one of them while they were just a few metres away from the Line of Control.  At this, the terrorists dispersed into the jungles and Singh led a search for them.  In the process, he sustained gunshot wounds and succumbed to the injuries.  He crawled forward to a boulder from where gunshots were fired at the soldiers.  He shot dead one more terrorist that pounced upon him.  The terrorist hid in a house nearby, but Singh climbed on the roof of the house and blew it up with grenades.  During the firing that followed, the terrorist hurled a grenade at Singh from which he suffered splinter injuries.  Unmindful of his injuries, Singh killed two more terrorists.  Later while being evacuated from the place, Singh succumbed to his injuries.  His team killed two more terrorists and eliminated the threat.  For his bravery, Singh was posthumously awarded the Ashoka Chakra, the highest peace time military decoration in India.

1980 Ispaster attack: The attack occurred on a Friday morning.  ETA had observed similar convoys from the factory and planned their ambush based on information that they had gathered.  The convoy consisted of four vehicles, the first carrying technicians, the third mortar devices produced by the factory and the second and fourth vehicles carrying three civil guards each.  The vehicle left the factory at 0730 and at approximately 0815, had to slow down at a part of the road which consisted of numerous bends.  The ETA members had chosen a spot near a small hill, where they were hidden from view by dense vegetation.  After allowing the vehicle carrying the factory workers to pass, ETA launched a grenade at the second vehicle, causing it to be stuck in a layby and then attacked the civil guard's vehicles with assault rifles, machine guns and grenades, firing over 100 shots.  In order to ensure that no civil guards survived, the ETA members approached the vehicles and threw a hand grenade into the first civil guard's vehicle.  When they repeated this with the second vehicle, two ETA members, Gregorio Olabarría Gorrotxategui Bengoa and Javier Argote, were killed as a result of injuries suffered when they failed to escape in time before the grenades exploded.  One of these was subsequently found 6 kilometres away from the attack, having apparently been moved there by his comrades.  At 0845, a man had approached a bar near the scene and had asked in Basque for medical assistance.

2011 Kashgar attacks: The 2011 Kashgar attacks were a series of knife and bomb attacks in Kashgar, Xinjiang, China on July 30 and 31, 2011.  On July 30, two Uyghur men hijacked a truck, killed its driver, and drove into a crowd of pedestrians.  They got out of the truck and stabbed six people to death and injured 27 others.  One of the attackers was killed by the crowd; the other was brought into custody.  On July 31, a chain of two explosions started a fire at a downtown restaurant.  A group of armed Uyghur men killed two people inside of the restaurant and four people outside, injuring 15 other people.  Police shot five suspects dead, detained four, and killed two others who initially escaped arrest.

2009 shootings of Oakland police officers: On March 21, 2009, Lovelle Mixon, a convicted felon wanted on a no-bail warrant for a parole violation, fatally shot four Oakland, California police officers.  Mixon initially shot and killed two Oakland police officers during a traffic stop.  After escaping on foot to the nearby apartment of his sister, Mixon then killed two police SWAT team officers attempting to apprehend him.  Mixon was then killed as officers returned fire.

Supporting paragraphs: Murders of Nicola Hughes and Fiona Bone Dale Cregan
Answer: Dale Cregan