The robbery was captured on video on Oct. 25 at 3:45 p.m., but authorities just released the video.
Houston police say the ATM technician told them that he was servicing the machine outside of a store in the 9400 block of Shady Drive when a gray, four-door sedan pulled up next to his vehicle.
A man got out of the passenger side of the sedan, walked around to the technician's vehicle, broke the window with a rock and removed an empty ATM cassette.
The man got back into the car, but just as the technician was about to intervene, another man pointed a handgun at him. The robbers then sped out of the parking lot.
The robber seen in the video was masked so police did not have a description of him other than that he was wearing dark clothing.
If you have any information related to the investigation, you're asked to contact Crime Stoppers of Houston directly at 713-222-TIPS (8477), submitting an online tip or through Crime Stoppers mobile app.
Information leading to charges or an arrest may result in a cash reward of up to $5,000, but tipsters must contact Crime Stoppers directly to remain anonymous and be considered for the cash payment.