Horror in Los Angeles as mother murders Air Force mechanic partner, 29, kills their baby and leaves the body on side of road with injured nine-year-old daughter before crashing into tree and killing herself

A Los Angeles mother murdered her partner in their ritzy apartment before killing their infant daughter and dumping her on the side of a highway with her nine-year-old half-sister in a horrifying murder-suicide.  

The shocking chain of events began at 4:30am on Monday when police were called to the 405 Freeway in Culver City where they found the body of an eight-month-old baby laying next to her nine-year-old sister on the shoulder of the road.  

The infant was pronounced dead the scene, and the nine-year-old girl was rushed to a hospital. 

Police found the body of their mother 15 miles away. She had crashed into a tree and killed herself. 

The mother, who DailyMail.com can name as 34-year-old Danielle Johnson, had left a grisly scene at the $5,600 home where she murdered her partner, Jaelen Allen Chaney, 29. 

 Jaelen Allen Chaney, 29, was found dead in his Woodland Hills, Calif. apartment Monday morning. Neighbors said they heard Chaney arguing with the woman he lived with just a few hours before he was killed

California Highway Patrol officials said an infant who was abandoned on the 405 Freeway in the Culver City area died at the scene, but her 9-year old was rushed to a hospital. Above, cops respond to the kids 

Police found the body of their mother 15 miles away. She had crashed into a tree and killed herself

He was found in the family's apartment by a neighbor who saw blood 'pouring' under the door. 

Los Angeles Police Department officials provided more details on Tuesday as to how the tragedy unfolded. 

Investigators said Chaney and Johnson were heard arguing at about 3:40 a.m. Monday, and at some point, the fight turned deadly when the 34-year-old stabbed her partner.

LAPD officials said the bloody knife Johnson used to stab Chaney was found at the home.

Johnson then fled from the apartment with her two children. 

Johnson's car was spotted on the 405 Freeway at about 4:30 a.m. when witnesses saw the infant and the nine-year-old pushed out of the running vehicle, LAPD said.

The baby died from her injuries sustained from the fall and the nine-year-old girl suffered moderate injuries.

Johnson then drove south to Redondo Beach at speeds over 100 mph when she plowed her car head-on into a tree at the intersection of Pacific Coast Highway and Vincent Street.

Chaney's grieving brother, Matthew Chiricas, told DailyMail.com his sibling had 'embraced' the older child from Johnson's from a previous relationship as his own. 

'I never seen him like kids, but I know he absolutely adored her.' 

What drove the woman to kill remains a mystery. 

Johnson's family member, who did not want to be identified, said the 34-year old was a stay-at-home mom.

'She sounded OK when I spoke to her last month,' the shocked family member said.

Neighbors said the couple had lived in the posh apartment for a little over a year with the two children. 

A neighbor told ABC7 she heard the couple arguing in the middle of the night. 

The next morning, she saw a trail of blood coming out of the apartment.

LAPD officials said Jaelen Allen Chaney, 29, was killed at his Woodland Hills apartment, which had some damage possibly connected to the murder

Cops are still investigating if the woman who was driving the vehicle and fatally crashed into a tree was connected to Jaelen Allen Chaney's murder 

Danielle Johnson, had left a grisly scene at the $5,600 home where she murdered her partner, Jaelen Allen Chaney

Chaney, who loved to travel and play video games, was in the U.S. Air Force for about four years, family members said

'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 walls,' she said.

The woman's father called 911. 

'Called the police and told them that something was not right,' the neighbor said.

'And they told me, when I spoke to the EMT, to go in and check on the body. So I did. 

'And he was deceased, he was facedown on the floor. And there was a lot of blood.'

Family members said Chaney was a mechanic for the U.S. Air Force and was stationed in Europe

Chiricas said his brother checked in with him sporadically, but never shared details of his relationship. 

In one concerning text message from November 2022, he said: 'I have been dealing a lot personally with my girlfriend that I don't care to really share right now because it's not appropriate. 

Chiricas said his brother and his girlfriend had traveled around Europe when he was stationed in Italy.

'The last message he sent to me was greeting me a happy birthday,' Chiricas said.

'He was in the Air Force, but he had dreams to become a weather man. He was just like the rest of us, trying to have fun and trying to have a family.' 

Police are yet to reveal the woman's motive or cause of death.  

The older girl was taken into the care of CPS.