LOS ANGELES — Police on Thursday identified the man they say carried out a murder-suicide that took the life of an engineering professor at UCLA.

The shooter was Mainak Sarkar, said Officer Jenny Houser, a city police spokeswoman. Sarkar is listed on a UCLA website as a member of a computational biomechanics research group run by the victim, a professor of biomechanical engineering.

The shooting Wednesday brought a massive police response and widespread fear of an active shooter among tens of thousands of people at the university. Now fear has shifted to sadness as many lament the death of a professor who worked on computer models of the human heart who was also a doting father who coached his young son’s baseball team.

Bill Klug, a professor of mechanical engineering, was gunned down in an engineering building office Wednesday, according to a law enforcement official with knowledge of the investigation but not authorized to publicly discuss it.

Finding the gunman’s motive in killing Klug will be foremost in the investigation as it continues Thursday.

Classes at the University of California, Los Angeles campus will resume Thursday for most of the school, and on Monday for the engineering department, whose students and faculty were coming to grips with his loss.

“Bill was an absolutely wonderful man, just the nicest guy you would ever want to meet,” said a collaborator, UCLA Professor Alan Garfinkel. “Devoted family man, superb mentor and teacher to so many students. He was my close colleague and friend. Our research together was to build a computer model of the heart, a 50 million variable ‘virtual heart’ that could be used to test drugs.”

Peter Gianusso, who headed the El Segundo Little League where Klug coached, said he “exemplified what Little League was all about: character, courage and loyalty.”

“He had a special relationship with his son through baseball, was a great coach, spent countless hours on the field with the boys and girls of El Segundo Little League,” Gianusso said.

The initial reports from the scene set off widespread fears of an attempted mass shooting on campus, bringing a response of hundreds of heavily armed officers who swarmed the campus.