The blast on the fourth floor of a research building in Boston’s Longwood area early Saturday morning caused no injuries and little property damage, but drew national attention amid the heightened tensions of the modern political climate, particularly at universities. Harvard has been locked in a policy battle with the Trump administration for months over perceived bias against conservatives, and over the past few years, protests have raged on college campuses in the area as left-leaning students push universities to cut ties with Israel over its actions in Gaza.
But no political motive was apparent in a seven-page probable cause affidavit filed by an FBI agent, and US Attorney Leah Foley declined to speculate on any motive, saying the investigation remained in its early stages.
Speaking at a press conference Tuesday afternoon, Foley alluded to the terrorist attack at the Boston Marathon in 2013 as she noted the fear these types of incidents can cause.
“Anxiety levels naturally rise when the public learns that an explosion was intentionally caused,” Foley said. “I would say those levels may rise even higher in the Boston area.”
Authorities said it does not appear that there’s any ongoing danger to the public.
Prosecutors did not move to hold either man while the case is pending. Magistrate Judge Jessica D. Hedges released both on conditions including that they stay away from Harvard and do not possess any dangerous weapons — including fireworks, the judge noted. Both hired private lawyers and are next due in court for a preliminary hearing Nov. 24.
Cardoza’s attorney, Stefan Rozembersky, said that the allegations don’t bear out a federal charge.
“This is a simple case of property damage,” he said.
In the affidavit, FBI special agent Erin O’Brien laid out a timeline of Cardoza and Patterson’s night on Oct. 31 into the early morning hours of Nov. 1, based on witness statements and surveillance footage.
The pair arrived at Wentworth Institute of Technology around 8 p.m., meeting up with several people who were going out to what the FBI agent describes as “Halloween social activities.” One person they went out with told police the pair had split off as the night grew late, saying they were headed to a party by Tufts University.
Cameras began to catch them in Longwood after 2 a.m., according to O’Brien. Footage on Longwood Avenue allegedly captured the pair walking toward the medical school campus around 2:23 a.m. wearing distinctive clothing. One, she wrote, was clad in a balaclava, a brown sweatshirt, tan pants, and white Crocs, while the other was in a blue mask, a dark jacket, and plaid pajama pants.
Around 2:24 a.m., they set off what appear to be Roman candle fireworks outside, footage showed.
A few minutes later, video footage from the Goldenson Building at 220 Longwood Ave. shows them climbing a chain-link fence and hopping into a construction area, the FBI agent wrote. Then, at 2:36 a.m., they’re spotted climbing scaffolding next to the building and getting onto its roof.
At 2:45 a.m., police received an alert that there had been an explosion on the fourth floor of the building, which houses a research laboratory that focuses on neurobiology.
They soon left the building, fleeing in opposite directions, according to video footage. The man in plaid pants — later identified as Cardoza — sat down on a bench and ditched the pants, taking them off and throwing them out in a trash bin, according to the FBI, citing more surveillance footage.
Beginning around 3:09 a.m., Patterson had returned to Wentworth and, according to more video footage, was running between buildings, trying to enter.
After he was able to get into one and charge his phone, he met back up with Cardoza and a third person who is not federally charged with any crime related to the explosion.
The trio tried but failed to get into another Wentworth dorm, footage shows, so they moved on to the nearby Massachusetts College of Art and Design campus, the FBI agent wrote. Patterson, too, began to take off his clothing, the FBI said.
By that afternoon, the pair headed back out of town, now to party at the University of Massachusetts Amherst.
As the explosion began to make headlines, several Wentworth students and guests told police they had information, and they quickly helped identify the pair. Patterson had told multiple people about how he had set off a cherry bomb in the Harvard building, according to the FBI.
One person said he heard the pair say they “chose a building that looked abandoned.” The affidavit did not quote any of the Wentworth students saying why the pair had done it.
Docks, the FBI special agent in charge, thanked the public “for their patience and cooperation.”
He continued, “We could not have gotten to this point today so quickly without their help.”
In the days since, school officials have said there was no structural damage to the building or the labs, and the fourth floor has been cleared for normal use.
The school has maintained vigilance regarding potential attackers for years.
Earlier this year, the university said it would pay security expenses for Harvard Hillel, a Jewish campus organization, amid fears of antisemitic violence.
In a separate incident, a New Hampshire man was sentenced last year to three years of probation after he was found to have brought a hoax device to Harvard’s Science Center Plaza in Cambridge in 2023. Investigators later found he had unwittingly been recruited to do so after answering a Craigslist ad, in a scheme allegedly orchestrated by someone else, who later called the university demanding a large amount of cryptocurrency.
Sean Cotter can be reached at sean.cotter@globe.com. Follow him @cotterreporter. Travis Andersen can be reached at travis.andersen@globe.com.
