"There is enough similarity in these cases certainly to cause us alarm," Darby said. "There's a good possibility these crimes could have been committed by the same offender."
The three cases, according to Darby:
* 11:45 p.m. April 25: A man approached a 23-year-old woman walking toward Tyson Avenue near Rowland, in Mayfair. Police say he threatened her by placing a sharp object to her neck and sexually assaulted her in a nearby driveway on Disston Street.
* 12:50 a.m. May 17: A man approached a 29-year-old woman on Wellington Street near Sackett, in Mayfair. When she began to scream, police say he held a sharp object to her neck. He tried to remove her clothing, but police say a neighbor came to her aid and the attacker fled. A neighbor filmed the incident.
* 10:30 p.m. Wednesday: In the most violent of the three incidents, police say a 20-year-old woman was grabbed and forced to the ground on Roosevelt Boulevard near Knorr Street, in Castor. He then dragged her behind Our Lady of Ransom Church, where police say he physically and sexually assaulted her.
Darby said the attacker is likely from the area and advised residents to keep driveway lights on.
Joseph DeFelice, legal counsel and past president of the Mayfair Civic Association, said the neighborhood watch is on alert.
"People are getting a little nervous, but we have a strong community and we will continue to look out for each other," he said.
Police plan to go door-to-door handing out detailed crime bulletins about the incidents.