SCHERTZ, Texas -

Two people were killed after a pickup truck slammed into the rear of an 18-wheeler in Schertz early Tuesday morning.

IMAGES: Fatal Schertz accident

Schertz police estimated the truck's speed at 60 mph to 65 mph at the time of the accident.

Police said they received a call for a reckless driver on Interstate 35 South at 3:24 a.m.

One minute later, the driver of the truck reportedly exited at a rest stop near Schwab Road and smashed into the 18-wheeler.

Both vehicles were quickly engulfed in flames and the two people inside the pickup truck died, police said.

The driver of the big rig was not injured.

Roberto Martinez was behind the wheel of the big rig. He said he couldn't avoid the impact, and Schertz police told him they couldn't prevent it, but an officer told him that he was trying.

"Somebody report that truck coming too fast on the freeway. He waited for the truck over there, ready to stop it," Martinez said.

IMAGES: Fatal Schertz accident

The crash happened just moments after police heard about the driver, before anyone could stop it.

Police are still trying to piece together what led up to the crash. The first call to dispatch provided few clues.

"The vehicle was all over the road, using, using their words. There were no other indicators of what may be going on," Schertz Police Sgt. Robert Martinez said.