The driver of the crash is Andrew Cassell, 25, of Eagle. He was arrested and is charged for vehicular manslaughter.
The crash happened just before 3 a.m. Friday morning on Highway 44 at mile marker 20, near N. Horseshoe Bend Rd.
(Photos from the Scene >>>)
The driver of the car was sent to Saint Alphonsus hospital with non-life threatening injuries and police say the passenger was confirmed dead on scene.
According to Idaho State Police Andrew R. Cassell, 25 of Eagle was traveling westbound on Highway 44 in a 2004 Kia Optima. Cassell left the roadway striking a power pole on the right shoulder.
As a result, Cassell's passenger Aldina Ekic, 21 of Boise, died at the scene. She was not wearing her seatbelt.
Idaho State Police say alcohol was a factor in the crash.
Troopers say costume material was found in the car and say the two may have been coming from a Halloween party.
"Again [it was] a tragic accident," said Idaho State Police Sgt. Sam Ketchum. "Someone [was] driving down the road, either not paying attention or under the influence, and now we have a young person that's dead."
State Street was closed for about an hour and a half after the crash but reopened before 5 a.m. for the morning commute.
Stay with KBOI for updates.