The officer was working a security side job at a jewelry store in the Post Oak Plaza shopping center on S. Post Oak Ln. at San Felipe when the shootout happened.
"As he was escorting a customer outside, he saw two black males in a silver four-door sedan pull into a parking lot, get out and immediately begin peering inside a Tahoe that was parked next to it," HPD spokesperson Kese Smith said.
Investigators say the nine-year veteran officer believed the men were about to break into the car, so he approached them.
Detectives say the suspects quickly jumped into their own vehicle and sped off, hitting the officer in the leg.
"The officer, at that point in time, fearing for his safety, discharged his duty weapon several times, striking the vehicle," Smith said.
Though several bullets hit the suspect's car, detectives are unsure whether the men inside were wounded.
Witnesses say the getaway car also struck and damaged a parked vehicle as it sped away from the scene.
The off-duty officer suffered a minor leg injury and is expected to make a full recovery.
Police say the sedan has tinted windows and will have noticeable damage from the bullets and the crash.
Anyone with information is urged to call HPD or Crime Stoppers at 713-222-TIPS.
Please stay with abc13.com for additional details as they become available.