Michael Barbar, 52, is accused of killing his wife, 43-year-old Maysam Barbar, and her 6-year-old daughter, Tamara Barbar.
Detectives say the couple's oldest child, an adult, was the one who called 911.
When detectives arrived at the scene on Banner Place in Perris Saturday, they found yet another child, a 10-year-old girl, alive at the scene. She might have seen the whole thing.
Detectives say Barbar fled the scene, and was found a day later in New Mexico.
"Sunday, we did have two of our detectives go out there and talk to him, where he is in custody in New Mexico. Now we're going to find out whether or not he'll fight extradition, so this way he can come back to Riverside County and be held for those two murders," said Riverside County Sheriff's Sgt. Dennis Gutierrez.
But if he was the one who killed his wife and step-daughter, what set him off? Two weeks ago, he seemed just fine.
"I see him walking down the street with his daughter, all the time, say 'hi' to him. He actually came up to my house on Halloween, he and his daughter were trick-or-treating," said Ray Reyes, a neighbor. "He was here for Halloween, and we started started talking to him, see how everything is going and everything like that."
Reyes says he thinks Barbar was going through a divorce, but wonders why the man would allegedly kill his wife and stepdaughter, but leave the other two kids alone.
"He seemed like a family guy and everything like that, and I think divorce just ended up getting to him and pushed him over the edge is what I think," said Reyes.
Grief counselors were on hand at Val Verde Elementary School, where 6-year-old Tamara Barbar was a first-grader.
"That's very shocking, especially when you find out a parent did it," said Amanda Lopez, a parent of a student at Val Verde. "Oh, I don't understand why a parent would do that. If you have problems, then go somewhere, but don't ever hurt a child. I don't understand why anyone would do that."
Authorities reportedly caught up with Barbar in New Mexico at a motel. Someone had noticed the license plate and description of his vehicle and called detectives. Riverside County Sheriff's deputies were there Sunday speaking with him. There is no word on whether Barbar will fight extradition.