Students from Tom Green Elementary School in Hays County, Texas were on their way home from a field trip when the fatal crash occurred.

According to the Texas Department of Public Safety, a concrete truck veered into oncoming traffic and hit the front of a school bus causing it to flip. As a result a car that was traveling behind the bus crashed into the disabled school bus, killing the driver.

The horrific crash left one child and an adult male dead. Dozens were injured.

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Court documents obtained by CBS Austin state Jerry Hernandez, 42, the driver of the concrete truck, admitted to smoking marijuana the night before the crash and consuming cocaine the morning of.

Hernandez also confessed to only sleeping three hours the night before the crash.

“As soon as I see the phrase 3 hours of sleep, that concerns me greatly,” said Lee Jackson, Crash/Accident Investigator and former Fort Worth Police Officer.

While reviewing the bus’ dashcam footage, Jackson commented: “It looks like he’s really right in the middle of the road and I don’t see the driver’s face at this point. Normally what you would see at this point, is the truck driver in complete panic mode; I don’t see that here which leads me to believe that he’s he’s drifted over the side of the road and he’s unaware of it.”

“Smoking marijuana, which of course is a depressant that’s going to make him more, much more likely to be falling asleep than anything else. The cocaine, of course, is a stimulant.”

“This should not have happened and there are families that are really seriously hurting right now,” he said.

The investigation is ongoing.