JEFFERSON COUNTY, Colo. (KDVR) — Moments before an 18-wheeler driver crashed his truck into stalled traffic in Lakewood two years ago, he called to say he was having brake problems.

The man who got that phone call was one of the witnesses Thursday in the trial of the driver, Rogel Aguilera Mederos, who’s charged with killing four people in a fiery explosion.

The driver was calling Rafael Perez Radrages to say his rig was in trouble.

Mederos’ 18-wheeler was out of control heading straight into stalled traffic on Interstate 70.

“He called me to tell me he was having problems with his brakes,” said Rafael Perez Radrages.

Radrages is also a truck driver and worked for the same Texas company as Mederos.

Radrages had previously driven and inspected the same rig that crashed.

Mederos has claimed the rig’s brakes were not working. But Radrages says there were no previous problems with the truck.

“It is the driver’s responsibility to check the truck and the trailer prior to the trip and during the trip. If you stop to put diesel in the truck, you need to check the truck,” Radrages told the court.

There were lots of questions about the type of training drivers get for mountain driving in the driving manuals.

Radrages said every driver must know how to use a rig’s braking systems and know when to stop and let them cool down when they are at risk of losing their stopping power.

Court adjourned with a diesel mechanic who inspected the 18-wheeler’s engine after the crash.