Deputies have a vague description of the suspects, so they're urging residents in the area to be viligant because they're considered to be armed and dangerous.
Harris County investigators say the armed robbery at the Atascocita Walmart may have been an inside job.
"To see if these two suspects had any type of information that came from inside the store that only employees would know; that's certainly one of the angles that our investigators will be looking at," Harris County Sheriff's Office Deputy Thomas Gilleland said.
Two men armed with a long gun and a rifle walked in at 11pm, the exact time when employees take the cash from every register and put into one cart.
"As they were doing this for each cash register, the two males entered the store," Gilleland said.
The robbers -- wearing cloths to conceal their faces -- made off with a large amount of cash in just a few minutes. Shoppers are now concerned about their safety.
"Well I've seen cops on every block basically and I didn't really know what was going on until we came up here to Walmart and we saw like four cop cars blocking off the entrance," shopper Charles Hines said.
"I am always watching behind me, in front of me, around me. I'm always watching my areas, never leave my back to a door," shopper Kristi Wittman said.
The men took off in a 1995 or 96 white Ford Taurus with a handicapped placard. They headed into the Eagle Springs subdivision, and that's the last place deputies say they saw them.
"It's just unnerving," another shopper said.
Walmart issued the following statement about the robbery:
"We're thankful no one was hurt and we appreciate the quick response of police. We have provided information ... and will continue to assist them in their investigation."
Anyone with information about this robbery is asked to contact Crime Stoppers at 713-222-8477.