Officers responded to the eastbound North Loop flyover at northbound Eastex Freeway at around 6:30 p.m.
According to police, no one witnesses a shooting, but people did stop on the flyover to check on the man and found him unconscious in his truck.
Shortly after, he was pronounced dead from an apparent gunshot wound.
Authorities said the passenger side window was broken.
Investigators are trying to determine if road rage was a factor in the shooting.
ABC13 has real-time traffic data to help you navigate Houston's roads and avoid traffic delays. Sign up for traffic alerts that are sent straight to your phone through our ABC13 app. Manage your notifications from the settings tab. Live traffic map