A 22-year-old man allegedly stabbed his mother in the chest while the two were on the 10 Freeway in Pomona Sunday night.
The incident was reported shortly before 10 p.m. in the eastbound lanes near Towne Avenue, according to a news release from the California Highway Patrol.
A witness who called authorities said they could hear a female screaming. A person was also seen throwing objects over the freeway onto an alleyway adjacent to the onramp, the CHP stated.
Arriving officers found the 22-year-old man, identified as Branden Lewis, and his 53-year-old mother, both suffering from stab wounds to their chests.
Investigators believe Lewis had stabbed his mother before throwing objects, including a knife, over the wall.
It was unclear how Lewis was injured in the incident.
A search of the alleyway turned up a cell phone, some credit cards and the knife, the CHP stated.
The vehicle was also taken for evidence in the investigation.
Both Lewis and his mother were transported to Pomona Valley Hospital in good condition.
Lewis will be facing attempted murder charges, according to the news release.