Authorities said 24-year-old Benjamin Colton Barnes from Riverside busted through a snow tire checkpoint and sprayed a park ranger's vehicle with bullets, killing Margaret Anderson.
After shooting Anderson, Barnes fired at another ranger before fleeing into the woods. After an extensive manhunt, Barnes was found the following day in a creek. An autopsy showed he drowned.
Police say Barnes showed signs of erratic behavior since returning from Iraq. They believe Barnes fled to the park after shooting and injuring four people at a house party in Seattle earlier that evening.
Admission to the park was free on Saturday. The flag remained at half-staff, and a small memorial for Anderson was at the rangers' kiosk.
Anderson left behind her husband, who also worked at the park, and two children. A candlelight vigil will be held in her honor on Sunday.
The Associated Press contributed to this story.