During a 20-minute phone call, Pasadena emergency services operator Diane Marin persuaded the caller to surrender, as another operator relayed information to officers who surrounded the house where he was holed up, authorities said.
Marin told a news conference that the man called Saturday and said, "'I killed someone.'"
Police say John Izeal Smith, 44, is suspected of killing 90-year-old Luis Fernando Aguiar inside a Pasadena house and Maria Teresa Aguiar, 59, outside the dwelling.
Neighbor Jose Hernandez Iribe, 31, was fatally shot when he ran toward Aguiar as she lay wounded outside, police said.
Two other people were grazed by bullets and shrapnel and treated for minor injuries, police said.
Smith also opened fire at officers and fired a total of 40 bullets before going back inside the house and calling 911, police said.
Marin, who said she had fielded emergency calls from neighbors reporting gunfire in the area, said the caller was evasive but eager to talk about himself.
In a recording of the final moments of the conversation. Marin is heard assuring the man, "They don't want anyone else to get hurt. They don't want you to get hurt also."
"I'm coming out," the caller says.
After the roughly 90-minute standoff, police took Smith into custody without firing a shot. No officers were injured.
It's unclear what motivated the shootings, but Pasadena Police Chief Phillip L. Sanchez said the two "themes" emerging in the investigation involve a possible landlord-tenant dispute and a possible long-term relationship between Smith and those living inside the home.
Smith legally purchased the two assault rifles and one semi-automatic pistol that were recovered from the scene, police said.
Smith was being held without bail in a Los Angeles jail and is scheduled for a court appearance Tuesday. It could not be immediately determined if he has a lawyer. Police said they initially erred in reporting Smith's age as 35.