HOUSTON -

Houston police officers are trying to determine if the same group of suspects are responsible for two violent robberies on the city's north side.

The first robbery happened at around 10 p.m. Thursday at the Star gas station off of the North Loop at Yale. A clerk said there were four total suspects involved. One stayed outside, while the other three went inside.

Security cameras rolled as one of the suspects pistol-whipped a customer and another suspect held the clerk at gunpoint. Another clerk was showing up for work while the men were inside.

"A very scary situation here. I came in at 10 p.m. to change shifts and I see four guys with a gun," said employee Alex George. "There were three inside and one guy pulled a gun on me and tells me, 'Go away.' I went around the street."

Police say the security cameras will play a key role in the investigation as officers continue to search for the men who ran away from the scene. Police say one of the suspects yelled 'Police!' leading the others to leave before they could access any money.

Officials say two customers filling up gas saw what was going on and drove off.

The second robbery was reported at a gas station at Airline and Sunnyside about a half hour later. Surveillance video shows three men running into the store, one then jumped the counter and demanded money from the register while the others pointed guns at customers inside the store. A customer was pistol-whipped before the suspects left the scene.

Police say in addition to money from the register, the suspects also stole one customer's wallet. A shot was also fired toward the cashier as the suspects ran out of the store. He was uninjured.