Rogel Lazaro Aguilera-Mederos, of Houston, is accused of causing last week's crash on I-70 that involved 28 vehicles.

JEFFERSON COUNTY, Colorado — The truck driver accused of causing a fiery crash on Interstate 70 last week that killed four people "knowingly engaged in conduct that created a grave risk of death," according to prosecutors.

Those prosecutors announced 40 charges against Rogel Lazaro Aguilera-Mederos on Friday. Shortly after, he appeared in court where he was advised of the charges. He's due back in court July 11 for a preliminary hearing.

They include 36 felonies and four lesser counts:

Four counts of vehicular homicide-reckless

Six counts of first-degree assault

24 counts of attempted first-degree assault

Two counts of vehicular assault

One count reckless driving

Three counts crime of violence (which is a sentencing enhancer)

"The charges that are filed reflect individual victims that were put at risk as a result of the actions of Mr. Aguilera," said District Attorney Peter Weir during Friday's press conference. "So there's a relationship between each count and a separate individual that either died, was seriously hurt or was placed in extraordinary risk of serious bodily injury or death."

As a result of the charges, Aguilera-Mederos faces decades in the department of corrections, Weir said.

The 23-year-old Houston man was initially arrested on four counts of vehicular homicide related to the crash that happened late in the afternoon April 25 in the eastbound lanes of Interstate 70. It involved a total of 28 vehicles, which included four semi-trucks and 24 passenger vehicles.

"Mr. Aguilera was observed .. at the general area of the Genesee Parkway, Evergreen exit at Lookout Mountain driving extremely fast and in a reckless manner," Weir said. "The speed limit for a commercial vehicle that Mr. Aguilera was operating, a semi-truck with a trailer is 45 mph. The estimated speed of Mr. Aguilera at that time and in subsequent times heading east on I-70 was in excess of 85 mph."

The crash killed four men:

Doyle Harrison, 61, of Hudson, Colorado

William Bailey, 67, of Arvada, Colorado

Miguel Angel Lamas Arellano, 24, of Denver, Colorado

Stanley Politano, 69, of Arvada, Colorado

Ten other people were hurt, two of them had serious injuries.

Politano’s wife, Cathi, told 9NEWS that her husband was the executive vice president for casino development company Jacobs Entertainment. He was a graduate of Wheat Ridge High School.

Family members described Lamas Arellano as a happy person with good intentions.

Crying, Lamas Arellano's mom said in Spanish that she tries to think positively, but right now she just can't. It's been difficult for her as a mother to forgive because nothing will bring her son back, she said.

Aguilera-Mederos was driving a semi-truck eastbound from the mountains on I-70 when he struck the back of stopped traffic near 6th Avenue, according to the Lakewood Police Department.

According to an arrest affidavit released last weekend, Aguilera-Mederos told investigators that his brakes failed prior to the crash.

The report says Aguilera-Mederos noticed his speedometer showed 85 mph. He told investigators he had to get over onto the shoulder to avoid stopped traffic, but when he tried to, another semi-truck was there.

That same report says because of the semi on the shoulder, Aguilera-Mederos decided to swerve back toward traffic. He said he thought he was going to die so he "closed his eyes before hitting the stopped traffic," the affidavit said.

Evidence of mechanical failure hasn’t been made public, but 9NEWS learned the truck company that Aguilera-Mederos works for, Castellano 03 Trucking LLC, has a history of safety issues with at least 10 violations for brake problems.

The semi-truck Aguilera-Mederos was driving was destroyed in the crash.

"There will not be a possibility to do a mechanical inspection," Weir said. "But there will be other means by which hopefully we can determine whether or not brakes were the cause of the accident or some other cause."

"We believe there was some sort of malfunction, and there's good evidence of that," Robert Corry, an attorney for Aguilera-Mederos, said last weekend. "This is a man who has no traffic offenses on his record. None, not even a speeding ticket that he was convicted of. No criminal record at all."

9Wants to Know was making efforts to reach someone from Castellano 03 Trucking for comment.

Two witnesses interviewed by law enforcement said they noticed what would turn out to be Aguilera-Mederos' semi-truck speeding past them near the buffalo herd overlook at Lookout Mountain. The pair of men said they followed the semi-truck and saw it driving in all three lanes and, at one point, it forced a pickup truck off the left side of the highway. Video provided by the witnesses show the semi-truck ignoring a runaway ramp, the affidavit says.

Following his arrest, Aguilera-Mederos' bond was set at $400,000 with several stipulations. He will not be allowed to drive a commercial vehicle, he must drive at all times with his license, he must not leave Colorado and he must surrender his passport, the First Judicial District Attorney's Office said.