The Houston Police Department said officers were flagged down by a motorist about the shooting on Sunday.
Officers said they discovered a man was killed near a gas pump on Scott Street.
Investigators believe the man was involved in some sort of argument with a woman when she shot him in the mouth.
The woman drove away after the shooting and hasn't been caught. But, officers say they believe they know the woman's identity.
It is unclear if the suspect and victim knew each other, and no other injuries were reported.
If you know anything about this case, authorities urge you to contact the Houston Police Department's Homicide Division at (713) 308-3600.