The suspect pulled a gun shortly after walking into the store in the 2300 block of South Kirkwood near South Lake last Friday, June 3, around 1:30 p.m.
Houston police said the robber placed a magazine in the gun, racked the slide, then started demanding money from the cash register.
Video released by HPD on Wednesday shows the robber clean out the register, then go looking for more cash in a back office.
He ordered one worker around the store, yelling at them to go to a safe.
Police said he fled the store in an unknown direction.
Before the robbery, surveillance video captured the robber changing his shoes outside.
He was wearing brown work boots before entering the store, but changed into black shoes for the robbery.
Police described the suspect as an 18- to 26-year-old man of an unknown race. He was wearing a gray hoodie, black pants, gloves and a mask.
Contact Crime Stoppers of Houston directly if you have any information related to this investigation. Information leading to the charging and/or arrest of any felony suspects may result in a cash payment up to $5,000. Tipsters must contact Crime Stoppers directly to remain anonymous and to be considered for a cash payment by calling 713-222-TIPS (8477), submitting an online tip at www.crime-stoppers.org or through the Crime Stoppers mobile app.