Baby found dead on Los Angeles highway linked to family's murder-suicide, police say

The death of a baby found Monday on a highway has been linked to a possible murder-suicide in Los Angeles, police told ABC News.

Early Monday morning, the body of an 8-month-old girl was found on the 405 Freeway. A 9-year-old girl was found on the shoulder, alive but with moderate injuries, according to the Los Angeles Police Department.

Shortly after, a woman -- who police identified as the children's mother -- crashed her car into a tree in Redondo Beach. She was pronounced dead at the scene, police said. Police identified her on Tuesday afternoon as Danielle Johnson, 34.

Authorities on Monday found the father dead from apparent stab wounds in an apartment in Woodland Hills. He was identified by police on Tuesday as Jaelen Chaney, 29.

Police said Tuesday that during the early hours of Monday morning, the two "became involved in a verbal altercation that escalated into Johnson becoming violent, stabbing Chaney, who succumbed to his injuries at scene."

A knife with biological evidence was recovered at the scene.

The mother is also suspected of leaving the two children on the highway and then crashing into a tree.

The two children were "expelled" from the car while it was moving, police said. It is not yet clear whether the baby was already dead or died later on the highway.

The 9-year-old girl, who is believed to be a witness to the murder, was hospitalized for her injuries and is now in safe custody, police said.

Neighbors told Los Angeles ABC station KABC they heard an argument coming from the apartment the night before and saw blood in the area the next morning.

"Their door was wide open, there was blood on the floor leading into their apartment, and then a trail of it in the hallway leading up to the elevator and I saw some blood on the wall," a 26-year-old woman told KABC.

The woman's father called 911, she said, who told them to check inside the apartment, where they found the man dead.

"He was deceased, he was facedown on the floor," she said. "And there was a lot of blood."

ABC News' Alex Stone contributed to this report.