2 men are charged with setting off fireworks inside an empty Harvard Medical School building

Hours later, they were escorted into U.S. District Court in Boston in handcuffs as relatives of at least one of them looked on. Judge Jessica Hedges asked if they understand the process, and both said they did. She then ordered them released pending trial and forbid them from possessing explosives or visiting Harvard while free.

Stefan Rozembersky, a lawyer for Cardoza, who is from the Cape Cod town of Bourne, said after the hearing that the case is one of “significant overcharging.”

“We’re dealing with property damage — this would ordinarily be a state charge,” he said.

Patterson, who is from the Boston suburb of Plymouth, left the hearing with his family, who declined to comment when approached by a reporter.

The explosion happened at around 2:45 a.m. Saturday on the fourth floor of Harvard Medical School's Goldenson Building, which houses labs and offices associated with the school’s neurobiology department. The building was empty and no one was injured.

“Let me be clear: Setting off an explosive device inside a locker at an institution geared toward higher education is not some harmless college prank. It’s selfish, it’s shortsighted and it’s a federal crime,” Ted Docks, the FBI’s special agent in charge, said at a news conference. He wouldn't speculate as to the motive.

According to the charging document, witnesses said the defendants were visiting the Wentworth Institute of Technology for Halloween activities, including parties at area schools. On the morning of the blast, surveillance footage captured the two walking toward Harvard's medical school wearing face coverings. Witnesses said the pair chose the building because it looked abandoned and got into it via the roof by climbing up scaffolding, the charging document states.

Witnesses said the pair lit a roman candle outside of the building and placed a cherry bomb inside of a locker in the building that then exploded, according to the charging document.

An officer who responded to a fire alarm that morning encountered two people running from the building, Harvard police said.

“Anxiety levels naturally rise when the public learns that an explosion was intentionally caused. I would say those levels may rise even higher in the Boston area,” U.S. Attorney Leah B. Foley said at the news conference, noting that the investigation is ongoing but that there’s no further threat to the university.

Medical school officials said the explosion caused no structural damage and that all labs and equipment remained intact. Investigators were able to identify Cardoza and Patterson after releasing suspect photos from surveillance footage and receiving calls from people who recognized them, authorities said.

This story was updated to correct the name of the Wentworth Institute of Technology, which was wrongly referred to as Wentworth College.