The shooting happened around 5 p.m. outside the Chipotle Mexican Grill on Texas Avenue near Main Street, close to the historic Rice Hotel.
Sources say the victim, identified in court records as Curtis Moore, is the son of a Harris County Sheriff's Office sergeant. The department confirms it is supporting the family during this time.
Witnesses told ABC Houston affiliate KTRK that the suspect, Nicholas Youngblood, 21, had been selling cookies on the sidewalk before the violence erupted. Court records list a cookie business as his employer.
Those who work nearby say Moore delivered food in the downtown area for online delivery companies and was a familiar face.
Video shared shows Moore arriving on a bicycle outside the restaurant. A verbal exchange appears to take place before the suspect, dressed in all pink, pulls out a gun and fired. KTRK paused the video before the shooting.
Investigators are looking into whether the suspect took issue with how Moore looked at him prior to the confrontation.
Houston police responded quickly and took Youngblood into custody nearby.
Records state he shot at the victim nine times.
Youngblood has been charged with aggravated assault with a deadly weapon, a charge that could be upgraded if the victim dies from his injuries.
Prosecutors are asking that Youngblood not be granted bond. A judge is expected to consider that request during a court appearance scheduled for Tuesday.
The investigation remains ongoing.