Two good Samaritans told officers they spotted the man walking on Hollister near West Tidwell around 12:30 a.m. and were trying to find out what had happened to him when the shooter appeared, investigators said.
The shooter walked up and shot the bloodied man, killing him.
The two bystanders were not hurt.
There was no word on the shooter's description or the victim's identity.
If you have information about the victim or the shooting, call 713-222-TIPS (8477) or submit a tip online at www.crime-stoppers.org.