The Oregon mall shooter was dressed all in black and his face was covered by a white hockey mask.
The mask, the black clothes, the age of the gunman and a weapon are becoming a familiar and deadly pattern.
The gunman, 22-year-old Jacob Tyler Roberts of Portland, is one of a string of killers before him, including Aurora shooter James Holmes, who chose to wear black and cover their faces with masks.
For these cold-hearted killers, the costume bolsters their confidence and power as they carry out their depraved fantasies, said Dr. Mary Ellen O'Toole, a retired FBI profiler.
"They're doing it because it's a role. It's almost like a big game and like they're the puppet master. They've got the control, the power, the weapons," she told ABCNews.com.
"The biggest thing for a mass shooter is the control and empowerment for the shooting," said former FBI agent and ABC News consultant Brad Garrett. "It isn't uncommon for a shooter to wear a costume, or sometimes simply to dress in black.... He went there being someone other than who he is in reality because it gives him power."
From the costume to his age and ethnicity, Roberts fit the mold of who FBI profilers expected the shooter to be.
"Its clear the majority [of shooters] are white males, but we can't say anything statistical about that," O'Toole said, pointing to the Virginia Tech shooting, which was perpetrated by a Korean, and the Red Lake shooting, where the gunman was Native American.
Nevertheless, she acknowledged the preponderance of whites among the list of mass killers.
"I think it's a question that needs to be put out there," O'Toole said
There is one thing that can be predicted, however -- age. Most mass shooters are between the ages of 15 and 25, O'Toole said.
"This is where we see young men acting out in a different way," she said, citing increased levels of testosterone. "It has to do with their biological make-up and development."
Garrett said that the age period between 15 to 25 years can also be a time when young men might feel the world is passing them by, stifling what they could have been. The desire to be remembered, he said, can be a factor that can cause unstable young men to kill.
They may have thoughts of, "I can be more than I am if you didn't stop me," Garrett said, adding that the "you" didn't necessarily refer to a specific individual.
Psychiatric issues are another commonality with mass killers, said Garrett.
"The idea that you can walk into a mall or any other location and shoot people is very intoxicating for these people. They typically do not feel empowered during the day," he said. "Depression, manic depression play into feelings of inadequacy."
As Roberts walked through the Clackamas Town Center, intent on killing as many people as possible, witnesses said he was looking straight ahead, shooting along the way.
Two people were killed and one wounded before Roberts took his own life.
While investigators try to piece together what made Roberts snap, O'Toole warned the cycle of gun violence will continue.
"Somewhere, there is a male in this age range thinking of outdoing the shooter in Aurora and outdoing the shooter in Oregon and they are watching this and saying, 'I am going to do it.'"
ABC News' Colleen Curry and Jared Weiner contributed to this report