HOUSTON -

Houston police are searching for the three armed men they say robbed a McDonald's off Highway 290 at Mangum late Tuesday night.

Officials say at the time of the robbery, the store was open and there were four customers inside.

“Three males came in, displayed weapons, robbed four customers and then robbed the store,” explained Larry Crowson with the Houston Police Department. 

After robbing the customers, detectives say one of the gunmen went behind the counter and demanded the store manager open one of the cash registers.

“Apparently the manager didn’t open the cash register fast enough. One of the suspects hit the manager over the head with the gun, and caused a minor injury. The suspects got some cash and then fled on foot,” Crowson said.

Police are looking at security video from the McDonald's in hopes of gathering more information. The suspects had their faces covered with masks and hoodies over their heads and police admit it’s going to be hard to track the men down.