Question: Steve "The Rifleman" Flemmi and John Connolly were both convicted following an investigation into corruption and other criminal activity within which U.S. government agency?

Context paragraphs:
Arlington Asset Investment: Arlington Asset Investment Corp is a principal investment firm that acquires and holds a levered portfolio residential mortgage-backed securities ("MBS"), consisting of agency MBS and private-label MBS.  Agency MBS include residential mortgage pass-through certificates for which the principal and interest payments are guaranteed by a U.S. government agency or government sponsored enterprise ("GSE") such as Fannie Mae and Freddie Mac.  Private-label MBS, or non-agency MBS, include residential MBS that are not guaranteed by a GSE or the U.S. government.  The company was formerly known as Friedman, Billings, Ramsey Group Inc. (FBR Group).  The company is headquartered in Arlington, Virginia.  It was founded in 1989 and had assets of over $4.1 billion as of December 31, 2016.  Arlington Asset Investment is an internally managed company and taxed as a C Corporation for U.S. Federal tax purposes, whereas many of its peers are taxed as a real estate investment trust (REIT).

Beetham Estate Gardens: Beetham Estate Garden is a neighbourhood in eastern Port of Spain, Trinidad and Tobago south of Laventille and northeast of Sea Lots elongated west to east between the Beetham Highway and the Eastern Main Road.  Formally it is located in the area of Laventille in San Juan-Laventille, but it is administred by Port of Spain.  Formerly, a slum called rat town, the community evolved as a residential area to some extent.  The area still has squatters living in the vicinity.  In 2008-9 the government built a four foot (1.2m) high wall around the 'gardens'.  The official reason was to protect the residents from traffic noise, but some suggest it was rather to contain criminal activity within the Beetham gardens community.

Stephen Flemmi: Stephen Joseph "The Rifleman" Flemmi (born June 9, 1934) is an American gangster and close associate of Winter Hill Gang boss Whitey Bulger.  Beginning in 1975, Flemmi was a top echelon informant for the Federal Bureau of Investigation (FBI).  Despite delivering a great deal of intelligence about the inner workings of the Patriarca crime family, Flemmi's own criminal activities proved a public relations nightmare for the FBI.  For this reason, he was prosecuted under the Racketeer Influenced and Corrupt Organizations Act (RICO) and sentenced to a long term of incarceration.

Detailee: A detailee is an employee of a United States executive branch government agency temporarily assigned to another position, generally in another U.S. government agency or an international organization.  The employee's original agency will usually continue to pay the person's salary.

National Background Investigations Bureau: The National Background Investigations Bureau (NBIB) is a semi-autonomous U.S. Government agency housed within the United States Office of Personnel Management (OPM) that is responsible for conducting security clearance investigations into individuals who need to hold security clearances for employment purposes.  Creation of the agency was announced in January 2016.  NBIB is the primary service provider of background investigations for the U.S. Government and conducts approximately 95 percent of government-wide background investigations for more than 100 federal agencies.  The agency's background investigation information technology (IT) systems will be designed, built, secured, and operated by the United States Department of Defense.

Law enforcement in the Netherlands: Law enforcement in the Netherlands is provided by the National Police Corps (Dutch: "Korps Nationale Politie" ), divided in ten regional units and a central unit, and the Royal Marechaussee (Dutch: "Koninklijke Marechaussee" ), a gendarmerie.  Law enforcement in the Netherlands operates primarily through governmental police agencies.  The law-enforcement purposes of these agencies are the investigation of suspected criminal activity, referral of the results of investigations to the courts, and the temporary detention of suspected criminals pending judicial action.  Law enforcement agencies, to varying degrees at different levels of government and in different agencies, are also commonly charged with the responsibilities of deterring criminal activity and preventing the successful commission of crimes in progress.  The Chief of Police (hoofdcommissaris) in The Netherlands is Erik Akerboom since March 1, 2016.  In recent years the majority of local councils have employed their own Enforcement officers or "Handhaving".  These officers have Special Enforcement Officer (SEO) status (Buitengewoon Opsporingsambtenaar) or BOA in Dutch and therefore have limited police powers (detaining suspects, ask for identification, make warrant less arrest, issue fines within their power of offences and use force). The majority of BOA officers have the authority to carry and use handcuffs which can only be issued to officers who have the power to use force.  A few councils also issue their officers, with permission from the Ministry of Safety and Justice, police batons and occasionally pepper spray.  Their main task is to enforce local ordinances, municipal code infractions, nuisances caused by noncriminal youth, several light traffic offences and anti-social behaviour.  All these tasks are sometimes called "Enforcing the Small Standard," meaning offences without a criminal undertone and enforcing primarily non-threatening situations.

Timothy A. Connolly 3rd: Timothy A. Connolly 3rd (born May 27, 1958), aka "Timmy Connolly" and "TC", is a former South Boston bar owner and mortgage broker, who wore a wire inside the infamous Winter Hill Gang and helped the federal government indict their two leaders, James "Whitey" Bulger and Stephen Flemmi ("The Rifleman").  The public was led to believe that Tim Connolly was merely a businessman and an innocent victim of one of Jim Bulger's many extortions.  But in truth, Tim Connolly was secretly a "made member" of the Winter Hill gang and a high ranking lieutenant in this Bulger crime family.

Law enforcement in the United States: Law enforcement operates primarily through governmental police agencies.  The law-enforcement purposes of these agencies are the investigation of suspected criminal activity, referral of the results of investigations to the courts, and the temporary detention of suspected criminals pending judicial action.  Law enforcement agencies, to varying degrees at different levels of government and in different agencies, are also commonly charged with the responsibilities of deterring criminal activity and preventing the successful commission of crimes in progress.  Other duties may include the service and enforcement of warrants, writs, and other orders of the courts.

John Connolly (FBI): John Joseph Connolly Jr. (born August 1, 1940) is a former FBI agent who was convicted of racketeering, obstruction of justice and murder charges stemming from his relationship with James "Whitey" Bulger, Steve Flemmi, and the Winter Hill Gang.

National Special Security Event: A National Special Security Event (NSSE) is an event of national or international significance deemed by the United States Department of Homeland Security (DHS) to be a potential target for terrorism or other criminal activity.  These events have included summits of world leaders, meetings of international organizations, presidential nominating conventions and presidential inaugurations.  NSSE designation requires federal agencies to provide full cooperation and support to ensure the safety and security of those participating in or otherwise attending the event, and the community within which the event takes place, and is typically limited to specific event sites for a specified time frame.  An NSSE puts the United States Secret Service in charge of event security, the Federal Bureau of Investigation in charge of intelligence, counter terrorism, hostage rescue and investigation of incidents of terrorism or other major criminal activities associated with the NSSE, and the Federal Emergency Management Agency in charge of recovery management in the aftermath of terrorist or other major criminal incidents, natural disasters or other catastrophic events.  NSSE designation is not a funding mechanism, and currently there is no specific federal "pot of money" to be distributed to state and local governments within whose jurisdiction NSSEs take place.

Supporting paragraphs: John Connolly (FBI) Stephen Flemmi
Answer: FBI