Two of the perpetrators, Nam The Tham and Siny Van Tran, were convicted of murder in 2005 after a decade-long international manhunt led to their 2001 extradition from China to the United States via Hong Kong.

[3][13][5] According to Assistant U.S. Attorney Susan Hanson-Philbrick, Pham was a rising star in Asian American organized crime in the late 1980s.

[3] Siny Van Tran (aka "Toothless Wah") was born in Vietnam before growing up in China and working as a sailor and a cook.

[3] No motive has been officially established, but initial police reports indicated a conflict between Chinese and Vietnamese gangs vying for power in Boston Chinatown in the aftermath of the late 1980s decline of Ping On.

[16] However, Tse was jailed in 1984 for sixteen months[9] after refusing to answer questions about an apparent unity ceremony he carried out with the heads of other triad organizations in Hong Kong.

[17][18]: 90–91  Tse responded to the subpoena from the President's Commission on Organized Crime by asserting his Fifth Amendment right against self-incrimination; after he was granted immunity in exchange for testimony, he continued to refuse to answer questions and was found in contempt.

[19] The power of the Ping On waned in his absence, and in 1986 Tse was forced to negotiate a peace with Cao Xuan Dien, the leader of the Vietnamese gangs in Boston.

[9] In December 1988, Cuong Khanh "Dai Keung" Luu demanded $30,000 from a Ping On gang member in Boston for undelivered fake green cards.

[21][22] While Tse remained in Hong Kong, Luu began gathering gang members in New York in January 1989 in a retaliatory assassination attempt on the Ping On leaders in Boston.

High-ranking Ping On members were aware of the plot, and Tse safely returned to the United States in May 1989 and October 1990 with Pham.

[14]: 54–55 On the night of January 11–12, 1991,[5] at approximately midnight, Young arrived at the social club and was admitted by Chung Wah Son (aka "Four Eyed Guy").

[24]: 4 After waking up around 4 am, the sixth shooting victim, Lee, crawled away from the massacre, dragged himself through a back door to a parking lot, and shouted for help; a passing couple noticed he was bleeding and alerted one of the two security guards at the NEMC ER.

[8]: 11 The three perpetrators, Pham, Tham, and Tran, drove to Atlantic City to gamble for a few days before escaping to Hong Kong on a United Airlines flight from Philadelphia International Airport via Tokyo[25] three weeks after the massacre.

[3][12][14]: 57–58  During the trial, purchase records and passenger manifests for three round-trip airline tickets with consecutive serial numbers were produced; the first was in the name of "Nam The Tham", departing from John F. Kennedy Airport to Hong Kong via Narita on January 31, 1991; the second and third were for "Hung Tien Pham" and "Wah Tran", departing on February 1 with identical routing.

[3][26] A grand jury had indicted "Toothless Wah" Tran and "Ah Cheung" Tham for their roles in the massacre on June 29, 1999.

[8]: 2  After delicate negotiations, the Chinese authorities agreed to extradite the two men in exchange for Qin Hong, a fugitive wanted in China for millions of dollars of fraud, who was arrested in New York by the FBI in April 2001.

[3][12][13][14]: 58 After they arrived in Boston on December 22, Tran waived his Miranda rights and provided a tape-recorded statement with his version of the events of January 12, 1991.

[8]: 3 In January 2011, Tham and Tran appealed their convictions in the Massachusetts Supreme Judicial Court on the basis of prosecutor pressure on the juries and the use of unauthenticated airline flight records.

[31] Paul F. Evans, who was Boston Police Commissioner and investigated the scene at the time of the massacre, called it "one of the most violent crimes that I’ve seen in my 30 years with the department".