The man who carried out a murder-suicide at the University of California left a "kill list" at his home that led authorities to find a woman's dead body.
Los Angeles Police Chief Charlie Beck said Mainak Sarkar drove to Los Angeles from Minnesota with two guns and killed Professor William Klug before killing himself.
Mr Beck said that when authorities searched Sarkar's home in Minnesota, they found a "kill list" with the names of Mr Klug, another UCLA professor and a woman.
He said the woman was found shot dead in her home in a nearby Minnesota town. The other professor on the list is unharmed.
Mr Beck said it appeared that mental issues were involved and said Sarkar's dispute with Mr Klug appears to be tied to Sarkar thinking the professor released intellectual property that harmed Sarkar.
Police are asking the public's help to find the car Sarkar drove to Los Angeles, a 2003 Nissan Sentra with the licence plate of 720KTW.
Mr Klug was gunned down in an engineering building office, according to a law enforcement official.
Classes at the University of California, Los Angeles campus will resume on Thursday for most of the school, and for the engineering department, whose students and faculty are coming to terms with the loss, on Monday.
"Bill was an absolutely wonderful man, just the nicest guy you would ever want to meet," said 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."
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.
Groups of officers stormed into buildings that had been locked down and cleared hallways as police helicopters hovered overhead.
Advised by university text alerts to turn out lights and lock doors where they were, many students let friends and family know they were safe in social media posts. Some described frantic evacuation scenes, while others wrote that their doors were not locking and posted photos of barricaded doors.
After about two hours, city Police Chief Charlie Beck said it was a murder-suicide and declared the threat over.
It was the week before final exams at UCLA, whose 43,000 students make it the largest campus in the University of California system.
Those locked down inside classrooms described a nervous calm. Some said they had to rig the doors closed with whatever was at hand because they would not lock.
Umar Rehman, 21, was in a maths sciences classroom adjacent to Engineering IV, the building where the shooting took place. The buildings are connected by walkway bridges near the centre of the 419-acre campus.
"We kept our eye on the door. We knew that somebody eventually could come," he said.
The door would not lock and those in the room devised a plan to hold it closed using a belt and crowbar, and demand ID from anyone who tried to get in.
Scott Waugh, an executive vice chancellor and provost, said the university would look into concerns about doors that would not lock.
UCLA's commencement ceremonies and end-of-year events will now include mourning Mr Klug, who was a devout Christian and a regular figure in organising spiritual life on campus.
In 2012, according to the campus website, he moderated a forum that his family and friends might find useful now called Does God Care?: Seeking the Meaning of Life in the Midst of Suffering and Death.