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Updated November 4, 2025, at 1:41 p.m.

Two men face federal criminal charges in connection with an explosion last week at Harvard Medical School, authorities announced Tuesday.

The FBI’s Boston office announced the arrests on social media Tuesday morning ahead of a press conference with Massachusetts U.S. Attorney Leah B. Foley.

The explosion occurred shortly before 3 a.m. Saturday on the fourth floor of the Goldenson Building, which houses HMS lab and office space. HUPD officers who responded to the call reported two individuals fleeing the area, and the department later released photographs captured on surveillance footage.

18-year-old Logan D. Patterson of Bourne and 20-year-old Dominick F. Cardoza of Plymouth were arrested Tuesday morning for their alleged involvement in the explosion, Foley announced at the press conference.

The two allegedly set off a Roman candle firework on the fourth floor of the building, Foley added. The firework detonated inside a research laboratory locker on the fourth floor, which houses HMS’s Department of Neurobiology, according to Foley.

Foley did not detail a possible motive for the explosion and said it was “just too early for us right now to speculate.” She described the investigation is “ongoing” and said that further information would not be immediately released beyond criminal complaints filed Tuesday. She also declined to answer reporters’ questions on where the two men had acquired the firework and whether they had spoken about their actions.

“There’s no doubt that these men allegedly did, in conspiring to commit the deliberate and extremely dangerous act, could have resulted in casualties had the Goldenson building been occupied at that time,” FBI Special Agent in Charge Ted E. Docks said.

Patterson and Cardoza face federal charges of conspiracy to damage, by means of fire or an explosive, an institution receiving federal financial assistance. According to an affidavit filed by FBI special agent Erin O’Brien, Patterson and Cardoza went to the Wentworth Institute of Technology campus, near HMS, for Halloween parties on the evening of Oct. 31.

The two men crossed the Charles River Friday night to seek out parties at Tufts University or MIT, according to several witnesses cited in the affidavit, but later returned to Longwood. One witness reported that Patterson and Cardoza showed him a video of the HMS explosion the next morning.

Foley said that authorities made the arrests after members of the public identified the suspects from surveillance images released Saturday. According to Foley, the suspects fled the building shortly after the explosion and discarded “distinctive items of clothing.”

The Boston Fire Department’s Arson Unit determined on Saturday that the explosion was intentional, but did not find additional explosives. The building, including the fourth floor, was open to affiliates on Monday.

A small section of the fourth-floor hallway was impacted, but no structural damage to the building had been reported, according to an email HMS Dean George Q. Daley ’82 and Executive Dean for Administration Lisa M. Muto sent to affiliates. No injuries were reported as a result of the explosion.

HUPD interim chief Denis G. Downing appeared at Tuesday’s press conference but did not take questions.

—Staff writer Abigail S. Gerstein can be reached at abigail.gerstein@thecrimson.com. Follow her on X @abbysgerstein.

—Staff writer Laurel M. Shugart can be reached at laurel.shugart@thecrimson.com. Follow them on X @laurelmshugart.