THERE'S A KILLER on the loose.

He is a cold-blooded, remorseless, compulsive, homicidal maniac. He does not fit the profile of the armed and dangerous thugs whose random acts of violence litter our streets with the bodies of men who look just like them.

A strangler is a special breed. His psyche is so grotesquely bent that he can look into the eyes of his victims as he squeezes the life out of them and feels them go limp in his hands.

They are, at the same time, frightening and fascinating, so bizarre that we struggle to find a rationalizing element to bring them into clear focus.

There is none. A man like the Kensington Strangler or Stranglers who murdered Elaine Goldberg on Ruth Street near Hart Lane in early November or who killed Nicole Piacentini less than two weeks later on Cumberland Street near Jasper may be behind you in the checkout line, seated next to you on the bus or unlike anyone you ever met.

Composite photos, even the detailed descriptions from victims who survived their encounter with what looks to be a single suspect, tell us only that he looks like a lot of men we pass on the street.

He may already be a serial killer, if it turns out that Allison Edwards, whose body was found on Glendale Street near Erie Avenue in Juniata Park on Friday, met her death at his hands. Three surviving sexual-assault victims in the same general area may have been targeted by this depraved strangler.

A serial killer is one who commits at least three murders with a cooling-off period. The FBI defines serial killings as "involving an offender associated with the killings of at least four victims over a period greater than 72 hours."

Police have not yet attributed Edwards' murder to the same man. But her mother told the Daily News that Edwards knew one of the victims.

"It could be that [Edwards] knew the killer, too," Karen Emery said of her daughter.

Even if Edwards' killer was someone else, there is a man on our streets who has killed without remorse and will likely kill again.

We ascribe superpowers to people who get away with murder again and again. To hear us tell it, Ted Bundy was an evil genius who led a corps of supersleuths and profilers on a fruitless chase.

But he was nabbed by a uniformed cop who pulled him over for speeding. This "genius" was caught with a rape kit in the trunk of his orange Volkswagen.

Despite what we've seen in movies and on TV, FBI profilers rarely catch serial killers. The killers do something stupid to get spotted by the public or nabbed by the kind of police work cops here do every day.

Police have called in a "forensic profiler," Lt. Ray Evers told me yesterday. But the heavy lifting is being done in the precincts.

"We have Homicide, Special Victims Unit, vice and both the 26th and 24th districts on this," Evers said. "There is a large group of officers working to get as much information as we can."

Evers acknowledged a pattern in the choice of victims, the method of homicide and the location of the crimes that link at least the two earlier homicides and three nonfatal sexual assaults.

There was also a DNA match linking the first two homicides to a single perpetrator.

"That has been put in the national database," he said. "Numerous suspects have been swabbed for DNA."

Police are also investigating a series of sexual assaults of women who were exiting cabs near Broad and Fairmount and recent reports of a man groping women in that same area.

"We caution women in those areas to try to walk in groups or with another person," Evers said.

Be sure to share that warning with the women you care about.

That may be the best we can do to protect them when there's a killer on the loose.

Send e-mail to smithel@phillynews.com or call 215-854-2512. For recent columns: http://go.philly.com/smith