PROVIDENCE — Detectives are especially concerned about an armed robber who held up Atwells Mini Mart on Federal Hill last week.

During the holdup he “racked” his semiautomatic pistol several times, pulling the slide back on top of the handgun, according to Capt. Hugh T. Clements Jr., detective commander.

That motion causes a shell to move from the magazine into the firing chamber of the gun.

“This was a dangerous robber. We’d like to have this guy identified so we can apprehend him and take him off the street,” Clements said yesterday.

A surveillance video of the robbery was provided to a television station to enlist the public’s help in identifying the suspect, and still photos from the video were printed on a flier that is being distributed by patrol officers, Clements said.

The robbery occurred at the store at 196 Atwells Ave., at the intersection with Dean Street, shortly before 11 p.m. Thursday.

Shree Ram Parajuli, 24, of Providence, the clerk, said a man pointed a silver semiautomatic handgun at him and began yelling and demanding money from the cash register.

At one point, the robber grabbed the register, Parajuli and a witness told the police.

The robber escaped with a box of cigars and approximately $1,100.

The suspect was described as white, approximately 6 feet tall, wearing a dark hooded sweatshirt and a bulky black and white camouflage jacket.

Another would-be robber was unsuccessful in Silver Lake Sunday night. Abdul Qayoum, 50, of Providence, owner of Sam’s Food Mart, 50 Pocasset Ave., Silver Lake, reported to the police that a masked man threatened him with a knife and demanded money from the cash register.

The proprietor said he pulled a bat from beneath the store counter and the suspect ran away empty-handed.