A Texas man was critically injured Thursday night when he tried to "roof surf" atop a car traveling down a highway, police said.

The unidentified man, 24, has life-threatening injuries after trying to climb out of a Scion xB and onto its roof. He fell from the car onto the highway but was not struck by any vehicles, authorities said. The man was transported to a hospital by helicopter.

The accident remains under investigation, and authorities are still looking for another passenger who fled the scene, Arlington police Lt. Michael Holguin said.

The driver did not appear to be intoxicated, but police believe alcohol may have been a factor, Holguin said.