The slain body of Edgar Guerrero was found just before 2 a.m. behind an apartment building off North Hacienda Boulevard in the 15000 block of Loukelton Street, said Los Angeles County Department of Coroner spokeswoman Courtney Morrow.
Los Angeles County homicide investigators are in charge of investigating the fatal shooting. They did not return calls for comment.
Two stray bullets pierced a living room window above where Guerrero's body came to rest. One continued through an adjacent living room wall before coming to a stop.
The apartment's resident was in bed at the time. He was not injured.
Guerrero was hanging out with two friends who live in the apartment complex, said his cousin, Jesse Guerrero.
Witnesses, who did not wish to be identified for fear of retaliation, said two teenage gang members walked into the apartment complex and asked Guerrero and his friends where they were from.
One of the teens produced a handgun from his waistband and opened fire, as Guerrero and his friends ran away, witnesses said.
Guerrero was pronounced dead at 2:12 a.m., Morrow said.
The shooting that claimed Guerrero's life was the area's third in seven days.
On Sunday afternoon a car was shot several times in an apparently unprovoked attack in East Valinda. Its occupants, a mother, father andtheir infant child were not injured.
No arrests have been made in the Sunday shooting, Los Angeles County Sheriff's Lt. Hiroshi Yokoyama said.
In yet another area shooting last week, a 29-year-old man sustained a bullet wound to his left leg.
The man and his girlfriend were standing in the parking lot of California Elementary school in West Valinda Monday evening when the shots rang out.
Deputies have yet to make any arrests in that shooting, Yokoyama said.
Guerrero's family members said the teen did not belong to a gang.
He attended La Puente Alternative High School.
"He was having some trouble in school, but he was getting his act together and spending a lot more time at home with his family," said Guerrero's god mother, Maria Gonzalez.
Guerrero enjoyed boxing and loved his three dogs, Gonzalez said.
The teen celebrated his 16th birthday on May 20, Gonzalez said.