PHOENIX, Az. (NBC NEWS) – A San Diego woman was stabbed to death at the scene of a bizarre car crash on an Arizona highway.
Police say it happened Friday morning on the 101 freeway in a Phoenix suburb.
After the car veered off the highway, police say the driver stabbed a female passenger inside the car and again when she managed to get outside the car.
Investigators say Martha Thy was stabbed or cut at least 20 times and later died at a hospital.
Witnesses stopped to help.
Someone tackled the man with the knife and others helped pin him to the ground.
Police say they took 25-year-old Fernando Acosta of Phoenix into custody on suspicion of premeditated first-degree murder and aggravated assault.
Investigators did not mention a possible motive.