AUSTIN (KEYE) — The driver of a semi-truck charged in the fatal 18-vehicle crash on Interstate 35 was under the influence of central nervous system depressants when he plowed through slowed traffic, according to an arrest affidavit.

Solomun Weldekeal Araya, 37, faces multiple counts of intoxication manslaughter following the Thursday night crash that left five dead, including two children, and 11 others injured.

According to the arrest affidavit, a detective and member of APD's Impaired Driving Investigation Unit determined Araya was impaired by CNS depressants, which are known to "slow down signals sent between the brain and the body."

Mr. Weldekeal Araya had droopy eyes, appeared drowsy, had slow and deliberate movements, appeared sluggish, and was acting very calm and relaxed given the circumstances of the collision," the affidavit stated.

Officers noted Araya's vital signs remained "unusually calm" for someone involved in such a traumatic incident. His heart rate and blood pressure were "on the lower end of normal range," which investigators found suspicious.

"Normally a person involved in a collision would experience physiological conditions such as an elevated heart rate and increased blood pressure, especially in a collision of this magnitude," the affidavit said.

The crash occurred at 11:21 p.m. in a construction zone where three lanes merged into one. Witnesses reported seeing the semi-truck continue for a tenth of a mile, striking multiple vehicles without slowing down.

According to the affidavit, four deceased individuals were in the same vehicle. First responders said the damage to the car was so severe, it looked like "an unrecognizable crumpled mess."

During field sobriety tests, officers observed six out of six possible clues for impairment during horizontal gaze nystagmus testing, along with multiple other indicators of intoxication.

While Araya claimed his brakes failed, commercial vehicle inspectors found no mechanical issues with the truck. Records showed Araya had multiple previous hours-of-service violations and prior hazardous moving violations while operating commercial vehicles.

The National Transportation Safety Board has opened a safety investigation into the crash.