BROOKLINE, Mass. (AP) — Police intensified their search Wednesday for a suspect in the fatal shooting of professor Nuno F.G. Loureiro at the Massachusetts Institute of Technology, who was shot at his home earlier in the week.

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 ongoing and no suspects were in custody as of Wednesday morning.

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 still 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.

Loureiro, who joined MIT in 2016, was named last year to lead MIT’s Plasma Science and Fusion Center, where he aimed 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.

Loureiro, who was married, 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, it 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.”

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.”

Some of Loureiro's students visited his home, an apartment in a three-story brick building, Tuesday afternoon to pay their respects, the Globe reported.

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.”