Austin police are looking for the driver of a car that caused a fiery crash Friday morning, killing one person and injuring three others. That driver left the scene

A second man who was critically injured in that crash was taken to Brook Army Medical Center in San Antonio with severe burns over much of his body.

It was a horrific scene for witnesses who first heard a series of explosions and later watched flames engulf a truck and then a helpless man.

Some frantic drivers heading northbound on Interstate 35 were the first to call 9-1-1.

"I saw a man in the middle of the street caught on fire completely on fire," said Christian Gamez, a Good Samaritan who used his shirt as a tourniquet to help stop the bleeding of the man on fire. "If I touched him on the arm, his skin was coming off. Like, I could have felt it right here."

A Texas Department of Transportation traffic camera caught images of the flames and subsequent explosions of fuel tanks and tires.

While Austin police continue working out the details, they believe a one-ton pickup with a trailer attached was disabled on the shoulder.

The trailer was rear-ended by a box truck after it was cut off.

"Witnesses said that a small white vehicle cut off the box truck and caused it to swerve onto the shoulder, at that point the box truck struck the back of the trailer. The trailer immediately caught fire," said Senior Police Officer Veneza Aguinaga, Austin Police Department.

The wreckage shut down northbound Interstate 35 for two hours and traffic was diverted onto Airport Boulevard and Cameron Road.

Anyone with information about the incident should call APD Vehicular Homicide Unit detectives at 974-6981.