Disguised in Halloween masks and black bandannas, an armed team of two men and a woman have orchestrated robberies at four Prince George's County businesses in recent weeks, police said, including one that led to the shooting and wounding of a 34-year-old convenience store clerk.

The armed robberies -- three at 7-Elevens and one at a hair salon -- have netted hundreds of dollars, police said, and disturbed investigators because of the brazen tactics and escalating threats of violence.

"There's a real urgency in trying to identify and apprehend the suspects because there is no sense of what they are capable of doing," said Cpl. Diane Richardson, a county police spokeswoman.

In each case, Richardson said, the robbers demanded money from employees after brandishing a silver handgun. They fled each time with undisclosed amounts of cash. She said the face of at least one of the assailants was covered during each of the robberies, usually with a costume mask.

The most recent robbery occurred about 2 a.m. July 4 at a 7-Eleven in the 6800 block of Livingston Road in Oxon Hill. One robber wore the mask of a skull, the letters "RIP" etched into the forehead. Richardson said that crime was committed by two men.

In grainy images captured on surveillance video, the masked robber is seen in shorts and a long white T-shirt standing near the register, his left arm tucked into his shirt and against his chest, perhaps to conceal an injury or identifying mark, police said. The second robber is unmasked, wearing a New York Yankees cap and pointing a small silver handgun at the store's 47-year-old clerk. The robbers fled on foot with cash and several packs of Newport cigarettes, Richardson said.

The first case was June 29. About 4:15 a.m., a woman disguised in a white Halloween mask and a man who wore a hooded shirt with his left arm wrapped in a white makeshift sling announced a robbery at a 7-Eleven in the 7500 block of Old Branch Avenue in Clinton. The clerk, who was not identified because he is a witness, was shot at. He suffered a graze wound to his head. The pair fled on foot with an undisclosed amount of money.

The next robbery occurred about 12:20 p.m. the next day at Marcheric Hair Gallery in the 5800 block of Allentown Way in Camp Springs. Several people were inside when an unmasked man and a bandanna-clad woman "burst through the door . . . shouting and using lots of profanity" demanding purses and money from salon patrons, owner Rochelle Ray said.

Ray, who was sitting at a desk preparing a deposit slip for the previous day's receipts, said the woman pointed the gun at one of the hairstylists. In all, the pair stole three purses and the nearly $600 that Ray, 40, had planned to deposit.

"It all happened within 20 or 30 seconds," Ray said, "but life will never be the same. We now lock the door as soon we get inside, and we have to buzz customers in and out. It's real sad how this can happen."

Another robbery attributed to the team of bandits occurred about 2:20 a.m. July 2 at a 7-Eleven in the 6500 block of Coventry Way in Clinton. In that robbery, the female robber's face was covered in a black bandanna, and her male accomplice wore a black hat that left his face exposed. Richardson said the man pulled out a small silver handgun and demanded money from the clerk. The pair fled on foot with an undisclosed amount of cash.

Police urge anyone with information about the cases to call the department's Crime Solvers at 800-673-2777.

The second robber wears a skull mask with "RIP" on the forehead. The men fled with cash and cigarettes.Surveillance video from a 7-Eleven on Livingston Road in Oxon Hill shows a robber pointing a handgun at the clerk.