DETROIT (AP) — Tony Leno was taking a smoking break outside the Toledo, Ohio, church where he works when a tall, muscular white man pulled over in his Chevy Blazer, got out and asked him for directions.

As the 59-year-old custodian turned to point the way, the stranger — apparently without word or warning — stabbed him twice in the abdomen, got back into his vehicle and drove off into the night.

Authorities say they’re not certain, but they strongly suspect the assailant is a serial killer who has attacked 20 men in Michigan, Ohio and Virginia since May, killing five and wounding others, including Leno, who remains hospitalized in critical condition.

The first 16 attacks happened in and around the working-class city of Flint. The city is predominantly black, and even though all but two of the Michigan victims were black men, detectives there have been hesitant to say the attacks were motivated by racial hatred. Survivors said their assailant said little during the attacks — and nothing about race.

But authorities in Leesburg, Va., a predominantly white city where three of the most recent attacks occurred, believe the three victims there were chosen because they are black.

WATCH VIDEO ON THE SERIAL SLASHER:

“I believe his motivation is pure hatred,” Leesburg Police Chief Joseph Price said at a Tuesday news conference in which he released a short video clip of the vehicle the suspect drove after attacking a 19-year-old man with a hammer. He said police also have footage of that attack but won’t be releasing it.

Federal and state law enforcement agencies trying to track down the killer have been reluctant to disclose details of what they’ve found out, and they haven’t released most of the names of those targeted.

State Police First Lt. Patrick McGreevy, who heads the Michigan task force investigating the attacks, declined to say much about the case on Tuesday but said investigators are poring over state prison records and past cases that are similar in nature.

“A nationwide intelligence broadcast has gone out, and we’re monitoring any incoming information from any state,” McGreevy said. “We don’t know what is in his head. What we do know is there has been a string of very, very violent and deadly attacks in Genesee County, and attacks in Leesburg that are similar.”

N. G. Berrill, the executive director of the New York Center for Neuropsychology & Forensic Behavior Science, who has studied serial killer behavior but who is not involved in the current case, said authorities are working against the clock to try to prevent further attacks because the suspect is unlikely to stop on his own.

“It’s a run rabbit run phenomena,” said Berrill, who compared the current case to the spate of knife attacks to the Beltway sniper case in which 10 people were shot to death in a three-week period in the Washington, D.C. area.

“They are not intending on receding into the darkness,” Berrill told The Associated Press on Tuesday. “They are on a spree and they are going to continue until somebody stops them. Because he is on this spree and going to a couple of different states, I don’t know if they can predict where he is going next.”

Michigan authorities said they didn’t realize they were dealing with serial killer until Aug. 4, more than two months after the first suspected attack on May 24 in Flint. Since then, the attack in Ohio and the three in Virginia have been linked to the assailant.

The brazen nature and the frequency of the attacks — the assailant has struck an average of about once every four days since the first stabbing — has terrified some of those in cities he’s already targeted. Officials have said there was about a month gap between the first two attacks.

Ira Lewis, a 77-year-old black General Motors retiree from Flint, said he’s taking no chances and will drive where he needs to go.

“People are being more vigilant and looking out,” Lewis said. “If he’s going to catch me, he is going to have to catch me in my car.”

Survivors tales have been similar: a white man who asked for directions or help with a broken-down vehicle suddenly pulled a knife, stabbed them then drove off.

Investigators have believe the suspect is a young, muscular white man, who drives a green Chevy Blazer, and they’ve compiled a composite sketch of his face.

“People are on edge. This is a very violent, dangerous person,” McGreevy said.

Police initially said the victims all were older black males who appeared frail or small in body size.

Now, police report that the youngest Michigan victim was 17. The oldest was 60. They ranged in size from 5-foot-4 inches and 120 pounds to 6-foot-1 and 190 pounds. Two of the 16 men attacked in Michigan were white.

“You can’t ignore the possibility that this is stimulated by some type of racial; if not hatred, then preoccupation or obsession,” Berrill said. “There’s always some kind of a last straw, a final indignation, pure unadulterated racism.

“Maybe he sees something in the news that pisses him off with a black politician or a black criminal, or an African American at work that gives the individual permission to begin the crime spree.”

The case is unique because the victims primarily are black men — not women and children, who are generally more vulnerable — and murder does not appear to be motivation, Berrill said.

“When you think of men as victims of serial killers it’s usually a gay population,” Berrill said.

“Usually with serial killers, there is a prominent sexual dimension to the killings. That doesn’t seem to be obvious here,” he said.

The assailant also left witnesses.

“It wasn’t benevolence. I don’t think he was sloppy,” Berrill said. “To be seen and identified strikes me as a little strange. Why isn’t he sure they’re dead? Why does he leave them alive? That’s the part that baffling. Killing may not be the goal. Killing may just be the unfortunate outcome.”

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Associated Press writers Matthew Barakat in Leesburg, Va., and John Seewer in Toledo, Ohio, contributed to this report.

Copyright 2010 The Associated Press.