Authorities responded to a shots fired call in the 1400 block of El Sereno Avenue at about 10 p.m. and found the three shooting victims.
"All of a sudden I hear gunshots, five (or) six, then a woman scream," said one witness.
The men were rushed to an area hospital, where one man was declared dead. He was identified as 18-year-old Steven Ascencio of Pasadena, according to a coroner.
The other two men, ages 17 and 19, suffered moderate injuries. They were treated and released from the hospital, and police say they are not cooperating.
The shooting is believed to be gang related, police said, but it was unclear if the victims are gang members. Police say Ascencio lived in the house where his friends were hanging out at the time of the shooting.
A suspect description was not immediately available. Police say the shooting may have been a drive-by, and the suspects may have been in a white late-model SUV.