The cops hunting the Kensington Strangler know this. As they run down tip calls, pour over neighborhood surveillance footage and scour the desolate, depressed pockets of Kensington for something, anything, that could lead them to the killer, they wonder:

What is fueling the maniac who has murdered two women, maybe three, and possibly led him to choke and sexually assault at least three others? Every idea is in play. But chief among the theories police are investigating is that the strangler was infected with HIV from a prostitute and is now hell-bent on exacting lethal revenge.

"It's a good theory that we are aware of," Deputy Commissioner William Blackburn said last night. "We're trying to figure out why this individual is attacking females engaged in high-risk behavior. That's an idea that we cannot dismiss."

Serial killers are often motivated by ideas and urges that are sexual in nature, he said.

So as detectives continue to try to plunge the depths of the strangler's mind, they have to consider other possibilities, as well, including that he has taken items from his victims as souvenirs.

"There's nothing to indicate that any of them were wearing jewelry that was kept by the perpetrator," Blackburn said, "but it's an idea that we're not dismissing, either."

One thing is for sure: If DNA evidence collected from Casey Mahoney, 27, the East Stroudsburg woman who was found strangled and raped in a lot at Front and Tusculum streets on Wednesday, connects her killer to the slayings of Elaine Goldberg and Nicole Piacentini, investigators will be dealing with a monster the likes of which they haven't seen in a long, long time.

All three women were found partially nude in vacant lots, and Piacentini and Mahoney were found positioned face-down.

"I have almost 30 years on and I haven't seen something like this before," Blackburn said, noting that the strangler - if it is indeed one person - has struck numerous times in a highly concentrated area in Kensington over a short period of time, even as an all-out manhunt has been waged.

"I don't know how many people can say they've experienced a situation like this," he said.

Earlier in the day, police officials released new surveillance footage of a man who beat and choked a 33-year-old woman in an alley on Sergeant Street near Kensington Avenue early Dec. 6.

The alley was the site of a similar attack Oct. 31.

Capt. John Darby, of the police Special Victims Unit, said the man in the footage - a medium-built black man who had long sideburns and wore a hoody while carrying a white iPod - is a "person of interest" in the three murders and two other sexual assaults of women who were choked into unconsciousness. One of the surviving victims helped police create a composite sketch, which the man in the video closely resembles.

Darby said detectives found the new footage, which shows the man sauntering past the alley about an hour before the attack, by pouring over "hundreds" of hours of area surveillance footage. Darby said the man appeared to walk with a gait favoring his left leg.

He implored city residents to watch the footage, which is available at the Police Department's website, www.phillypolice.com, and contact investigators at 215-686-TIPS if they recognize the man.

"This is not a phantom. This male did not crawl into a hole," he said. "He's out there. He's interacting with others."

That thought continues to send chills down the spines of people in Kensington, where the strangler is a constant source of discussion and fear.

Yesterday, numerous residents claimed that they heard the strangler was out for revenge because he had been infected with HIV.

"He got burnt. Do you know what that means? It means he was with a hooker and she gave him a disease," said Joey Mershan, 30, who lives in Kensington.

"And now, he has ot nothing to live for cause he's probably going to die. So he's going out on top.

"He's going after as many white hookers as he can. Put yourself in his shoes, do you blame him?" Mershan asked.

Three homicide victims have now been tied to the Kensington Strangler, two through DNA evidence. Police are also looking into whether three choking cases are also tied to the Strangler.

* Nicole Piacentini was found dead on Nov. 13 on Cumberland Street near Jasper.

* Elaine Goldberg was found dead on Nov. 3 on Ruth Street near Hart lane.

* Casey Mahoney was found dead Wednesday in a lot at Front and Tusculum streets. They were found facedown, nude from the waist down.

* Early October. A woman claims she was sexually assaulted and choked into unconsciousness at a property on Cumberland Street near Jasper, where where Piacentini was found.

* Oct. 31. A woman claims she was sexually assaulted and choked into unconsciousness on Sergeant Street near Kensington Avenue.

* Dec. 6. A woman claims she was strangled, punched and hit in the head with a brick in the same alley where the Oct. 31 attack occurred.

Despite the small increase in homicides, FBI statistics released yesterday showed that violent crime overall in the city was down 6 percent in the first six months of this year compared to last year.

The rash of homicides began about 8:40 p.m. Sunday when John Day, 39, was shot in his head and chest on Locust Street near 54th in West Philadelphia. A second shooting victim, a 33-year-old unidentified man, was found a block away at Irving Street near 54th, police said. Both men are believed to have been shot by the same person, police said.

Day, of Emerald Street near Orleans, was taken to the Hospital of the University of Pennsylvania and pronounced dead at 10:15 p.m., police said. The unidentified second victim was in stable condition yesterday.

In another double shooting, about 10:30 p.m., on Jackson Street near 25th, South Philadelphia, Dimitry Bryant, 26, was shot in the chest and an unidentified 25-year-old man was shot in his arms and knees during a robbery, police said.

Both were taken to HUP, where Bryant, of Bambrey Terrace near 27th Street, was pronounced dead at 10:50 p.m., police said. The second victim was in stable condition at the same hospital.

The third shooting happened on 6th Street near Diamond, North Philly, about 3:45 a.m. yesterday, police said.

The victim, whose identity was not released, was shot once in the chest during a robbery and pronounced dead at 4:11 a.m. at Temple University Hospital, police said.

There were 24 more homicides at this time in 2008, according to police statistics.

Overall, the violent crime drop reflects a national trend of a 6.2 percent decrease in cities of more than 100,000, according to the FBI's Semiannual Uniform Crime Report.

Forcible rape dropped from 451 cases to 449. Robbery and aggravated assault decreased by less than 1 percent.

An ice-hockey game between high-schoolers in South Jersey resembled a full-on riot Friday night as police in Washington Township had to avoid flying trash cans, coins and spit.

Someone even brought a smoke bomb.

"People obviously got a little wrapped up in this game. They lost control," said Capt. Rich Leonard, spokesman for the Police Department in Washington Township, Gloucester County.

The mayhem took place about 9:30 p.m. during a game between youths from Washington Township and nearby Williamstown at the Hollydell Ice Arena.

Leonard said several fights broke out in the bleachers and that when a Washington Township officer attempted to intervene, he was spit on and trash cans and coins were thrown at him.

Multiple units from surrounding townships were called in to restore order, Leonard said, and officers cleared the bleachers for both teams. During the evacuation, Leonard said, someone set off a pyrotechnic device, believed to be a smoke bomb, in the lobby of the arena while it was full of officers and spectators.

The game was canceled, Leonard said, and no one was arrested. "I don't believe they were able to identify the perpetrators," he said.

Leonard said it wasn't the first time the department was called to the rink for problems between teams.

"Obviously, if someone brings a smoke bomb, that's a problem," he said.

A man who answered the phone at Hollydell referred all calls to a manager, who was unavailable.

Administrators with Washington Township and Williamstown high schools said ice hockey is a club sport and declined to comment on Friday's incident.

No one was injured.