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JEFFERSON COUNTY, Colo.–  The trucker suspected of causing a fiery crash that killed four people on Interstate 70 in Lakewood in April appeared in court on Thursday.

Rogel Aguilera-Mederos preliminary hearing got underway at 8:30 a.m. in Jefferson County.

During the hearing, there was a revelation of the existence of dash camera video from a state trooper showing Aguilera-Mederos semi speeding on an Interstate 70 shoulder. Then moments later, towering black smoke like a huge bomb had gone off, according to tweets from FOX31 Investigative Reporter Rob Low.

District Attorney Peter Wier showed a semi driven by Aguilera-Mederos cut across all three lanes of Interstate 70 rear-ending multiple cars instead of veering right onto a grass median, according to a tweet sent during the hearing.

The defense attorney for Aguilera-Mederos insists mechanical brake failure led to the Interstate 70 fatal truck crash, according to Investigative Reporter Rob Low.

Aguilera-Mederos is charged with four counts of vehicular homicide, six counts of first-degree assault and 24 counts of attempted first-degree assault. He is the only person accused in the April 25 crash that occurred near the Denver West exit of eastbound I-70. It involved 24 passenger vehicles and four semi-trailers.

On May 18, Aguilera-Mederos posted bail, which had been set at $500,000.

He was born in Cuba and was living legally in Houston before the crash.

Earlier this month, Aguilera-Mederos’ defense attorney Rob Corry said there is no risk of his client fleeing.

“He is committed to seeing this through, one way or the other,” Corry said.

According to an arrest affidavit, Aguilera-Mederos told investigators that the brakes on his semi failed and that he was going more than 80 mph at the time of the crash.

Investigators reviewed a number of videos that appeared to show Aguilera-Mederos out of control, including one filmed by Pedro Olvera. That video appeared to show Aguilera-Mederos passing a runaway truck ramp and signs warning truckers about steep grades as the interstate winds into the Denver area.

Another video captured by a YouTuber shows a semi speeding down the shoulder of the interstate moments before the crash occurred.