PHOENIX —  The Baseline Killer sometimes strikes up a conversation just before he attacks, authorities said Wednesday as they released new information about one of the two serial killers stalking the city.

The Baseline Killer's victims probably had a gut feeling something wasn't right but shrugged it off, said Phoenix police Sgt. Andy Hill. That means that in many of the killings and sexual assaults attributed to him, the victims had an opportunity to get away.

"People do get intuitive feelings, and they do need to follow those feelings," Hill said. Police have not said how all his victims were killed, but several were shot. Hill would not discuss further specifics.

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The Baseline Killer and another suspected serial killer known as the Serial Shooter have taken as many as 11 lives in recent months, sparking fear in the sprawling city. Police have created two task forces to investigate, and officials have collected $100,000 as a reward for information leading to the arrest of either suspect.

The Baseline Killer, named after the Phoenix road where the first crimes were committed, is believed to have killed six people since September and to have committed 11 separate sexual assaults and a series of robberies.

Hill advised people to leave or call police if they ever get a strange, gut feeling about something. Police would rather chase down a false lead than investigate another killing, he said.

Katherine Ramsland, a professor at DeSales University in Pennsylvania who teaches about serial killers, said there could be two reasons the Baseline Killer talks to victims before striking.

"He's probably checking out how vulnerable they seem, whether they're seeming to be on guard, armed with a weapon or alone," Ramsland said. "And he's picking out certain types of people who are satisfying something for him, fitting a particular criteria that fulfills his inner fantasies."

The Serial Shooter targets victims who are alone and shoots from a vehicle, Hill said. The Serial Shooter is linked to five killings and 16 non-fatal shootings since May 2005.