"This isn't somebody who just snapped," said Clinton Van Zandt, a former FBI agent. "This is someone who likes what they're doing. This is someone who is playing God. They're sticking their finger in the face of the authorities and society."
The gunman "is somebody who is cold, who is calculating, who has the skills and doesn't care who they hurt," Van Zandt said.
"Statistically, this is something white males normally do," he added. "(But) You don't want to exclude any race, any ethnicity because there is always the aberrant behavior."
Police have said they have little to go on except for a witness who saw two men leaving one of the shooting scenes in a white van. They said evidence indicated each victim died from a single bullet from a high-powered gun wielded by a killer some distance away.
Police were developing a profile with the help of the FBI, Montgomery County Police Chief Charles Moose said. The Bureau of Alcohol, Tobacco and Firearms also brought in a "geographical profiler" to help determine whether there is a pattern.
Moose said police were looking for a driver and a shooter, as well as the white van. Van Zandt said the pair likely dumped the van.
"That vehicle will be in a garage or a lake," Van Zandt said.
Robert K. Ressler, another former FBI profiler, likened the spree to that of Andrew Cunanan, the suspected killer of fashion designer Gianni Versace and four other people. Cunanan died in an apparent suicide on a Florida houseboat in 1997.
"You're dealing with not a serial killer, not a mass murderer, but a spree killer," Ressler said. He said serial killers go though "emotional cooling-off periods" that could span days or even months.
The experts said the suspects are also probably from the Montgomery County area. And both said such crimes are generally solved by eyewitnesses or friends who notice the suspects have disappeared.
"There are people out there right now who have suspicions," Van Zandt said.