PUEBLO COUNTY, Colo. -

The Colorado State Patrol is investigating a rollover crash that killed one man on Sunday morning in Pueblo County.

Troopers have identified the man as Robert Nation, 36, of Nebraska.

The crash happened around 6:45 a.m. on Interstate 25 about two miles south of Pueblo.

A 2007 Ford F-150 was traveling southbound when it went off the right side of the road, CSP said in a press release.  Nation then over-corrected to the left, causing the Ford to rotate counter-clockwise.

The Ford continued southbound in the median and rolled twice before coming to a stop.  Nation was ejected from the vehicle.

Colorado State Patrol said troopers believe Nation fell asleep behind the wheel.  He was not wearing a seat belt.