HOUSTON -

Two nights of robbery sprees have businesses on Houston's northwest side on alert.

Three men robbed customers and employees at a Hartz Chicken restaurant; it was one in a string of at least four robberies Wednesday night.

Employees say three men had their faces covered when they ran into the Hartz restaurant just after 7 p.m. Wednesday. Once inside, two of them jumped the counter, demanding cash from the register, and wallets and cell phones from employees and customers.

"They caught everyone off guard.  And with the gun already drawn, there's nothing you can do but to do what they say," one victim told Local 2.

At least four businesses on the north and northwest part of town were robbed between 7 p.m. and 10 p.m., including another Hartz restaurant in the 5700 block of Hollister, the Family Dollar in the 500 block of Crosstimbers and a Shell gas station at Tidwell and Highway 290.

It was the second time the Hartz on Hollister was robbed in just one week.

In the Family Dollar robbery, Houston police say three masked men walked into the store held the employees at gunpoint.

Officials said the suspects took money from the cash register. As the suspects were leaving, police said they grabbed a woman's purse in the parking lot and stuck a gun in her face.

The suspects got away before officers arrived and no injuries were reported.

While police haven't confirmed if all of Wednesday night's robberies are related, the suspect descriptions are similar -- three men who had their faces covered -- and in a couple of the cases were seen leaving in a dark vehicle.

The crime spree follows another string of robberies on Tuesday night, also in northwest Houston, when three to four armed men held up a Valero, a customer outside of an Advanced Auto, and a McDonald's.

Officers believe those three robberies Tuesday may have been related because of their proximity to one another -- and the suspect's method of operation -- but they haven't yet said if they believe the same suspects are responsible for Wednesday night's cases.

Whoever they are, employees are just hoping they'll be caught soon.

"These guys are armed. And someone will get hurt if they're not stopped," said the victim.

Police are reviewing surveillance video from several of the businesses that were robbed Wednesday night, trying to get more information that could help identify the suspects.

If you have any information that could help investigators, call Crime Stoppers at 713-222-TIPS.