As new details emerged on the alleged gunman in the nation's capital, CBS Atlanta spoke with a criminal profiler in Georgia.
Dr. Dave Davis delved into the mind of a mass shooter and explained what would motivate someone to commit such a cruel act.
Davis, a forensic psychiatrist and the medical director of Piedmont Hospital's Psychiatric Clinic, said the gunman may have been angry with the government, society in general or someone in particular.
In any case, Davis said, the gunman likely felt his anger outweighed the rights of others.
Police said Aaron Alexis, who they have identified as the gunman in the Navy Yard shootings that left 13 people dead, including himself, had a history of violence.
In 2010, Alexis fired a shot into the ceiling of his apartment in Texas, which he claimed was an accident, police said.
In 2004, Alexis shot out the tires of a construction worker because the man made fun of him, police said.
Davis said a man who would react so quickly and so violently is an intensely self-centered person, bursting with rage.
"They're angry and they're going to act it out. They come apart. They sit on the anger for a long time, then they explode," Davis said.
It is not clear why the gunman opened fire.
Police are investigating whether the trigger man worked with another man.
Davis said they may suffer from personality disorders, rigid, unhealthy ways of thinking and behaving that prevent them from relating to people in a normal way.
"The person thinks their grievances are better than anybody else's, they're more important. They're going to do something. They're going to change the world," Davis said.
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