Driver had THC in system when car slammed into parked semi, killing 3 teens

LYNNWOOD, Wash. -- Investigators say the teenage driver who slammed into a parked semi last year near Alderwood Mall was under the influence of THC at the time of the deadly crash. Three of four teens in the car, including the driver, were killed.

The crash happened around 4:00 a.m. July 26, 2017 on Alderwood Mall Parkway.  The car hit the semi with such force that it became wedged under the trailer and its top was sheared off.

The Snohomish County Medical Examiner’s Office identified the teens as Landon Staley, 16; Travin Nelson Phongphiou, 16; and Mikayla Sorenson, 15. All three were friends and students at Henry Jackson High School in Mill Creek.

Heartbreaking message from mother of teen killed in triple fatal crash

Snohomish County detectives on Friday said they completed the investigation -- indicating several factors contributed to the deaths of three teens.

"In addition to impairment, the driver was speeding, inexperienced, likely fatigued due to the time of day and in violation of his Intermediate License," the detective wrote. "This collision occurred within the first six months of the driver receiving his Intermediate License while he was not allowed to have any passengers under twenty years old and/or drive a vehicle between 0100-0500 hours.  Whether the driver fell asleep, was interacting with other passengers in the vehicle, changing radio stations, checking his cell phone or doing something else that caused him to drift off the roadway will never be known.

Read the report from the lead detective below:

The Snohomish County Sheriff's Office previously said it is legal for trucks to park trailers in the designated parking areas along Alderwood Mall Parkway, but that the trailer was not parked in the correct direction, as the front of the trailer was facing the direction of oncoming traffic. "That is a civil parking infraction," the sheriff's office said.