A former FBI profiler says it's possible the Phoenix serial shooter is looking for "intimacy" in his attacks, and could even be inserting himself into the investigation.

The suspect is accused of killing seven people in nine shootings so far.

RELATED: Full coverage of Phoenix serial shootings

When the shooter killed 19-year-old Manuel Garcia, witnesses said he yelled something at his victim.

According to police documents, the 16-year-old boy who survived a separate attack in central Phoenix also said the killer yelled at him.

Former FBI profiler Brad Garrett said it's part of the shooter's thrill.

"One of the things for him, maybe, is 'If I can get the person to look at me...', it makes it even more fearful, or heinous on his part. And it inflicts more fear in the victim before they get shot," said Garrett. "If they turn around, see him, and see a gun and get shot, that's far different from just getting blindsided."

Another piece of evidence -- shell casings have been found close to several victims. In the case of 12-year-old Maleah Ellis and the two women killed in front of their Maryvale home in June, the casings were even in the back seat of the car where they died.

"Now you have two pieces of information that would suggest he wants more, maybe, eye contact or intimacy with his victim," said Garrett.

Police documents also detail at least three attacks where witnesses reported seeing somebody with the shooter. In one of the Maryvale murders on April 1, a witness told investigators they saw a gloved hand holding a pistol out the back passenger side of the shooter's car.

According to Phoenix police, accomplices are unlikely, but they're not ruling it out.

Meanwhile, Garrett said partners would be one explanation for the shooter's access to multiple vehicles. While most witnesses have described the suspect driving a black BMW sedan, some have also pointed to a white or light-colored Lincoln or Cadillac style car.

"It would be unusual for these type of shooters to have more than one person involved, but not totally impossible," Garrett said. "It certainly would account for different vehicle descriptions that you've had at various scenes; that if there's one or two other people involved with the shooter, that may also be participating. They may have vehicles to allow the switch from one to the other."

Garrett said the killer will likely take more risks to keep up the thrill. There's even a possibility he could attend one of the street shooter community meetings police have held to update the public on the investigation.

"It's very possible that he would show up, maybe, in a disguise or in another way," said Garrett. "Because if you believe that he gets some thrill and excitement or empowerment committing these shootings, what more exciting thing to do than to go to a meeting where they're talking about you?"