Friends say the violence erupted in front of the couple's 2-year-old son. The suspect's 10-year-old sister was also reportedly home at the time.
The incident happened around 7:45 a.m. in the 8100 block of Celito Drive. Friends have identified the suspect as Giovanny Reyes. Friends say his ex-girlfriend, who is around 19 years old, had gone over to pick up their son when they got in an argument.
Police say the argument turned deadly when the suspect opened fire on his ex-girlfriend before turning the gun on himself. The ex-girlfriend was pronounced dead at the scene. The suspect was transported to a local hospital in unknown condition, according to Los Angeles County Sheriff's Department Lt. Steve Jauch.
According to friends, Reyes, who is said to be in his early 20s, is in extremely critical condition after shooting himself in the torso.
The couple's 2-year-old son had just celebrated his birthday on Saturday. He is in the care of his paternal grandmother. Neighbors say the former couple had a volatile and violent relationship and say police had been called to the home in the past when the woman used to live there.