BROOKLINE, Mass. (AP) — Police intensified their search Wednesday for a suspect in the killing of professor Nuno F.G. Loureiro at the Massachusetts Institute of Technology, two days after he was shot to death at his home outside Boston.

Loureiro, a 47-year-old physicist and fusion scientist, was shot Monday night at his apartment in Brookline, Massachusetts. He died at a local hospital on Tuesday, the Norfolk District Attorney’s Office said in a statement.

The prosecutor’s office said the homicide investigation was “active and ongoing” as of early afternoon Wednesday and had no update — earlier they had said no suspects were in custody.

The investigation into the MIT professor's killing comes as Brown University, another prestigious institution just 50 miles (80 kilometers) away in Providence, Rhode Island, is reeling from an unsolved shooting that killed two students and wounded nine others Saturday. Investigators provided no indication Tuesday that they were any closer to zeroing in on the gunman's identity.

The FBI on Tuesday said it knew of no connection between the crimes.

Dozens of people gathered outside Louriero’s building Tuesday night, many with candles in hand, to honor the professor’s life and support his family. Neighbors received paper notices attached to their doors with tape to place candles in their windows in Louriero’s honor. Some people cried and held each other, but most attendees were silent, their breath visible in the bracing cold. A few children rode scooters from their nearby homes to the gathering.

The killing happened when most MIT students were on winter break, and more than a dozen of them on the Cambridge campus on Wednesday didn’t want to talk about it. Most said they didn't know him.

A 22-year-old student at Boston University who lives near Loureiro’s apartment in Brookline told The Boston Globe she heard three loud noises Monday evening and feared it was gunfire. “I had never heard anything so loud, so I assumed they were gunshots,” Liv Schachner was quoted as saying. “It’s difficult to grasp. It just seems like it keeps happening.”

Loureiro, who was married, joined MIT in 2016 and was named last year to lead MIT’s Plasma Science and Fusion Center, where he worked to advance clean energy technology and other research. The center, one of the school's largest labs, had more than 250 people working across seven buildings when he took the helm. He was a professor of physics and nuclear science and engineering.

He grew up in Viseu, in central Portugal, and studied in Lisbon before earning a doctorate in London, according to MIT. He was a researcher at an institute for nuclear fusion in Lisbon before joining MIT, the university said.

“He shone a bright light as a mentor, friend, teacher, colleague and leader, and was universally admired for his articulate, compassionate manner,” Dennis Whyte, an engineering professor who previously led MIT’s Plasma Science and Fusion Center, told a campus publication.

The president of MIT, Sally Kornbluth, said in a statement that the killing was a “shocking loss.” The office of Portuguese President Marcelo Rebelo de Sousa also put out a condolence statement calling Loureiro’s death “an irreparable loss for science and for all those with whom he worked and lived.”

Loureiro had said he hoped his work would shape the future.

“It’s not hyperbole to say MIT is where you go to find solutions to humanity’s biggest problems,” Loureiro said when he was named to lead the plasma science lab last year. “Fusion energy will change the course of human history.”

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Associated Press writers Leah Willingham in Boston; Mark Scolforo in Harrisburg, Pennsylvania; and David Biller in Rome contributed.