Police said Dwayne Alexander, 49, died after the afternoon attack at the Job Corps facility on Lodi Place, which also serves as a dormitory. He had been stabbed multiple times and died at Cedars-Sinai Medical Center.
A 22-year-old man was arrested in connection with the stabbing. Police said the suspect, whose name has not yet been released, was living at the facility and learning job skills.
LAPD Det. John Skaggs said the attack happened in an office, but the motive was still being investigated.
"I guess he was being a little nasty, a little weird lately. I don't really know why he would snap," said Alex Osuna, a former Job Corps student.
About 100 students live in the dormitory. Many hugged each other and shed tears when they learned of the popular counselor's death.
"He got me into my room immediately and he showed me how to do everything here," said Johnathan Whitney, a former student at the center. "I never had a problem."
Osuna described him as a "nice guy" and a "father figure."
The Los Angeles Job Corps Center is a government-sponsored program designed for young people. It provides academic support, vocational training and a place to live at no cost to students.
It was previously reported that Dwayne Alexander was 59 years old, but police now say he was 49.