A mechanical and aerospace engineering professor was identified by students and colleagues as the victim killed Wednesday in an apparent murder-suicide at UCLA.

William Klug, a husband and father of two young children, was in an office inside Boelter Hall on the Westwood campus before 10 a.m. when he was reportedly shot and killed by an unidentified student who then took his own life, sources told NBC4.

Law enforcement officials told NBC News the shooting suspect was an engineering graduate student who apparently had a strained relationship with Klug and may have also been upset over grades.

A gun and a note were found near the bodies, LAPD Chief Charlie Beck said during an afternoon press conference.

Friends in Shock After Professors Murder

"I’m just outraged," said Renjie Li, a student who knew Klug. "I’m mad that someone would do that to a young professor who just started his career at UCLA. It’s just a shame."

Li took a computer science class from Klug. Li said he was one of the most approachable professors on campus.

"He was always there for us. I just really appreciate him being that type of person there when I’m in trouble doing my project or having trouble figuring out a problem," Li said. "He’s definitely one of my favorite professors here at UCLA."

Late Wednesday afternoon, friends of Klug were in shock at the El Segundo park where his son played Little League. 

Student of Slain UCLA Professor Speaks Out

"It's hard to even fathom it — to have your son grow up without a dad," Lance Giroux, a family friend, said as he broke down in tears. "Hoping the community can rally around that and help him out because he's going to need it."

Parents said Klug would come to little league games to cheer on the team, even if his kids weren't playing.

"It's hard," Michael Alcala, a friend of Klug's, said. "Everybody came down here to gather to mourn a little bit, to console each other."

Klug was also the father of a young daughter.

Student of Slain UCLA Professor Speaks Out

The shooting prompted an hours-long lockdown of the campus involving hundreds of officers.

According to his biography on the UCLA website, Klug received his Ph.D. from Caltech in 2003, his master’s of science from UCLA in 1999 and his bachelor’s from Westmont College in 1998.

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Klug also led the Klug Research Group in Computational Biomechanics at UCLA.

A GoFundMe account has been set up here to help Klug's family.