Efrem Ruben Lozoya, 38, of Pico Rivera, was charged with the two felony counts on suspicion of fatally shooting his ex-wife and seriously injuring her boyfriend.
The charges include a special allegation that Lozoya personally and intentionally discharged a weapon, which caused great bodily injury and death.
Lozoya was arraigned Wednesday, and it was continued to July 18. Prosecutors plan to ask for his bail to be set at $5 million.
He and his ex-wife, identified as Nereida Villanueva, have two children together and were divorced for several years.
On Saturday, authorities said Lozoya dropped off one of the children at Villanueva's apartment in Whittier, when he entered the residence and opened fire. It was unclear if the children witnessed any part of the crime.
Authorities said Lozoya fled the scene. Villanueva was pronounced dead at the scene and her boyfriend, who was in the home at the time, was taken to a hospital for treatment.
Lozoya later turned himself in, according to authorities.
If convicted as charged, he faces a maximum sentence of 75 years to life in prison.