CHICAGO (CBS) — A robber held up three women at gunpoint near Columbia College in the South Loop Sunday evening.

The robbery comes on the heels of a police community alert warning of armed robberies on the same block and nearby blocks, going back to mid-August.

In the latest incident, three women were on the sidewalk in the 800 block of South Wabash Avenue at 8:30 p.m., when someone wearing a white mask came up, police said.

The masked suspect took out a gun and demanded property, police said. The victims complied and the suspect ran off, police said.

No one was in custody late Sunday. Police were seen gathering evidence and interviewing witnesses outside the Peet’s Coffee & Tea Shop at 800 S. Wabash Ave.

Earlier incidents involved at least one offender displaying a handgun and demanding property. The assailants punched or pistol-whipped anyone victims who hesitated to give up property.

The offenders always fled on foot and were seen getting into a vehicle afterward, police said.

The earlier incidents happened at 8:53 p.m. Saturday, Aug. 17 in the 800 block of South Wabash Avenue; at 5:30 a.m. Monday, Aug. 26, in the 1000 block of South Wabash Avenue; at 12:50 a.m. Sunday, Sept. 1 again in the 800 block of South Wabash Avenue, and at 2 a.m. Wednesday, Sept. 11, in the 0-99 block of East 11th Street.

The community alert indicated that the victims gave varying descriptions of the suspects depending on the incident.

Anyone with information was asked to call Area Central detectives at (312) 747-8384.