PHOENIX -- A forensic psychiatrist has been helping the serial killers task force look for potential suspects and helping officers extract information.

Dr. Stephen Pitt said at Friday's news briefing that behavior is the best indicator of personality.

A newly released Phoenix police report is shining light on how the "Baseline Killer," who has stalked Valley streets for more than a year, interacts with his victims and changes disguises.

The person linked to 23 violent crimes, including eight killings, robs victims and instructs them not to look at his face, according to the report obtained by CBS 5 News.

The report reveals how the Baseline Killer is even suspected of sexually assaulting a pregnant woman last September. The 23-year-old victim was with her sister walking on 31st Avenue at night when he attacked both women, the report said. The woman later identified a suspect in a photo lineup, but he is not currently in jail, according to police.

The women said their attacker was a black male, had a round face, was very clean shaven and wore a sports hat.

In a separate incident, a woman attacked last November while dropping clothes at a donation drop box told police her attacker asked her to take him down to the corner because he'd just robbed a place.

The victim said the attacker was wearing a "Halloween costume" and "black plastic glasses." He ordered her to "drive at the speed limit so not to cause attention," then sexually assaulted her. The woman said he "sounded pretty smart."

In other crimes, victims said the attacker pretended to be a panhandler or a junkie, talking loudly and rapidly and appearing as if he'd been drinking. Other times he's bald or has short hair, shows a weapon or demands money, the report said.

"The suspect has been very careful to wear different disguises and different looks," said Phoenix Police Sgt. Andy Hill during a daily news briefing on Thursday.

One of the victims attacked by the Baseline Killer confirmed some of the man's erractic behaviors.

The Scottsdale woman told CBS 5 News she was groped and robbed at gunpoint last September after a late dinner with her then boyfriend George Lata near North 40th and Campbell streets.

Lata, a self-defense instructor, said he remained calm and got on the ground and gave the man what money he had.

The woman stayed in the car and also handed over the money the man demanded. "He was freaking out. 'Is that all you have? I'm a junkie. I'm a junkie,'" the victim recalled.

After the couple gave him more money, the man said something surprising. "He said, 'thank you,'" the woman said.

Afterwards, the victim said the man groped her and then ran away.

Police believe the Baseline Killer, who is also behind 11 rapes and eight robberies, is a man who is 25 to 30 years old, dark skinned, and possibly black or Hispanic. Police have said he changes his appearance with wigs and hats and wears long sleeve shirts.

The last crime connected to the suspect was committed June 29.

"Now more than ever, people need to remain vigilant," Hill said.

Officers said Thursday they have seen an increase in the number of leads. Silent Witness is offering a $100,000 dollar reward for information that leads to an arrest. The number to call is 1-800-343-TIPS or 480-WITNESS.

The Baseline Killer is one of two serial predator cases in the Phoenix area. In another, dubbed the "Serial Shooter" investigation, police arrested Dale S. Hausner, 33, and Samuel John Dieteman, 30, in connection with 37 shootings, including seven killings. Police believe the men took turns shooting random victims throughout the Phoenix area late at night and early in the morning.