Here is a timeline of how the string of horrific events unfolded across a time span of several hours earlier this week:
Overnight Sunday
Neighbors of Danielle Cherakiyah Johnson, 34, and Jaelen Chaney, 29, heard a loud argument coming from the couple's Woodland Hills apartment in the middle of the night.
3:40 a.m. Monday
According to authorities, Johnson is suspected of fatally stabbing Chaney, her live-in boyfriend, inside the residence before fleeing with her two young daughters in a dark-colored Porsche Cayenne. Johnson rammed the apartment building's garage gate as she drove away in the SUV, investigators said.
The 9-year-old girl witnessed the homicide, sources told Eyewitness News.
4:30 a.m.
The mother and the two children were in the SUV on the 405 Freeway in the Westchester area when Johnson slowed the moving vehicle, opened the passenger door and then told her daughter "to get out of the car, and when the daughter didn't do that she then forcibly pushed her out of the vehicle, in the middle of the freeway, while moving, while the 9-year-old was holding the 8-month-old baby," Los Angeles Police Department Lt. Guy Nolan said.
Baby's death on 405 linked to Woodland Hills homicide, and possibly Redondo Beach crash
The infant fell to the pavement and was fatally struck by a passing vehicle, authorities said.
Good Samaritans found the children on the freeway and called 911. Emergency responders pronounced the baby dead at the scene, and her older sister was transported to a hospital. The surviving child was later placed in the custody of Los Angeles County Department of Children and Family Services.
5 a.m.
After Johnson allegedly forced the children out of the car, sources said she headed south to Redondo Beach, where she reached speeds of more than 100 mph. The SUV slammed into a tree on the corner of an intersection and Johnson was pronounced dead at the scene.
7:30 a.m.
A 26-year-old woman, a neighbor of Chaney and Johnson who lives in the same building, discovered a bloody scene.
"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," the woman said.
Her father "called the police and told them that something was not right. And they told me, when I spoke to the EMT, to go in and check on the body. So I did," he said, adding that Chaney "was deceased, he was face-down on the floor. And there was a lot of blood."
Aftermath
The search for the motive in the horrific incidents is ongoing.
"The only witness we have for this crime now is the 9-year-old girl," Nolan said. "There's just very little information we have, other than: there was a verbal altercation that turned violent and it ended in tragedy."