PHILADELPHIA (Reuters) -- The Philadelphia killer known as the "Kensington strangler" has claimed his third victim, police said on Tuesday, officially classifying the assailant as a serial killer.
Police released DNA tests showing that the killer of Carey Mahoney on December 15 was the same person who raped and strangled two other women in November.
With three victims, the perpetrator is now officially classified as a serial killer.
"DNA recovered from the scene provided a positive match to the person who was dubbed the Kensington strangler," Philadelphia Police Detective Justin Frank said.
Earlier on Tuesday, authorities offered rewards totaling $37,000 for information leading to the arrest and conviction of the attacker.
"We are serious about getting this psycho off the streets of Philadelphia," said Mayor Michael Nutter at a street-corner news conference in the Kensington neighborhood where the attacks occurred.
Police said they have acted on more than 150 tips from the public in the case, and appealed for more help. But they warned against citizens justice after a local man was erroneously linked to the attacks on Facebook, and a crowd gathered around his house.
"We will not tolerate anyone taking vigilante action against this individual," Ramsey said.
The killer may also have committed three other sexual assaults in the neighborhood, in which the women escaped, police said.
A further three assaults have some similarities to the three killings and the sexual attacks, although it is unclear whether all nine are the work of the same person, said police spokesman Ray Evers.
"We are including them until we have excluded them," Evers said.
The cash rewards were announced on a Kensington street corner where one of the sexual assaults took place in early October.
In a vacant lot across the street stands a makeshift memorial to 35-year-old Nicole Piacentini whose November 13 murder has been linked by DNA evidence to the killing of the strangler's first victim on November 3.
Piacentini's photograph is surrounded by candles and teddy bears and a sign saying "RIP Nicole" spray-painted on a builder's board.
Deputy Police Commissioner William Blackburn said 154 swabs have been taken for DNA testing, of which 45 have been excluded. About 120 prostitutes and "johns" or male customers have been arrested since Mid-November in an investigation that involves the police department's homicide and special victims unit.
(Reporting by Jon Hurdle, Editing by Greg McCune)