It happened around 11 p.m. Wednesday outside the Valero gas station on Wayside near the North Loop.
Police said a group of people were recording some sort of video when they got into an argument with another group of people.
Someone pulled out a gun and shot a man in the head. He's in critical condition.
Police have not made any arrests.
Investigators are trying to find out if the gas station may have captured it on its surveillance video.