TUSTIN, Calif. (AP) -- Authorities don't know the motive in today's rampage of carjackings and shootings across California's Orange County.

Three people were killed before the gunman ended the rampage by taking his own life.

Police say the violence began when a young man shot a woman to death in a home. Several shootings occurred in the next hour at other locations. The victim of a carjacking wasn't hurt, but an innocent bystander was hit by gunfire and taken to a hospital.

There were reports that the gunman also opened fire at other vehicles on a freeway.

Police say a pickup truck taken by the carjacker began to run out of gas, so he stopped and carjacked a BMW -- shooting and killing the driver. Another person was killed during an additional carjacking.

Police say they located the gunman and tracked him into the city of Orange. When they tried to stop him, they say, he got out of the vehicle and killed himself.