The 36-year-old running back was driving his BMW motorcycle with a female passenger in Austin, Texas around 10:20 PM when he slammed into a minivan that was trying to make a left turn across his lane of traffic. Both Benson and his passenger, Aamna Najam, passed away.

The Travis Country Medical Examiner conducted an autopsy on Benson and determined he died from blunt force injuries combined with severe burn injuries from the ensuing fire.

According to the report, Benson suffered burns to the majority of his body -- including his face, neck, torso, arms, hands, thighs, etc.

Benson also suffered several broken bones in the crash including a rib, a fractured pelvis, multiple abrasions and lacerations and severe injuries to his hands and wrists.

The report says witnesses called 911 and desperately tried to put out the flames on Benson's body with clothes and a fire extinguisher.

Benson was initially responsive when paramedics arrived, but ultimately died on scene.

As for the toxicology report, Benson tested positive for THC -- 42 ng/mL.

Benson also tested positive for a small amount of alcohol in his system but we're told the number is more consistent with ethanol produced by the body during decomposition than alcohol consumed that night. In other words, officials do NOT believe he was drunk.

The presence of THC could open the door for a possible lawsuit against Benson's estate if Najam's family wants to pursue a wrongful death claim.

Benson was an incredible athlete -- he racked up more than 5,500 yards at the University of Texas and won the Doak Walker Award (top running back in the country) his senior year.

He signed a rookie deal with the Chicago Bears -- 5 years, $35 mil -- and was a key part of Chicago's 2006 NFC Championship team.