Officials responding to reports of "an assault with a deadly weapon" found Hernandez "with significant injuries to her upper torso," and determined she died at the scene.
Investigators believe the man assaulted the victim, then used a motorized scooter as a weapon. Authorities have not said if the suspect had any connection to the woman.
"I never heard of anything like this either," a neighbor told KTTV. "We've been living here for years, since '93, and this is the first time something like this has happened."
A person of interest was located by police hours after the incident. The man, who has not been publicly identified, was taken into custody without incident and booked for murder, and was being held on $2 million bail, police said.