Authorities said the shooter knocked on the door of the couple's apartment at the South Loop near Broadway just before 8pm Thursday.
The victim -- 29-year-old Guillermo Lopez -- let the man into the apartment and then was shot. Lopez doed at the scene.
Houston police said Lopez's wife and a neighbor both saw the attacker. He is described only as a Hispanic male in his late 20s, about 5 feet 7 inches tall and about 150 pounds.
No one else was injured. The victim's three children were outside playing at the time of the murder, police said.
At this time, there is no known motive for the shooting. If you have any information about the case, you are asked to contact the HPD Homicide Division at 713-308-3600 or Crime Stoppers at 713-222-TIPS.