No Remorse: The lack of remorse is probably one of the most striking signs of a shooter. They do unspeakable acts and display no regret.
Act Violently: Shooters don’t perform their first “big act” out of the blue. They tend to do little things along the way—whether it was hurting the family dog or other acts of violence so they can build up their violence muscle. It is really mental illness that can act so violently over and over again.
History of Social, Emotional & Mental disturbances: Shooters have a history of being socially inept, lacking in emotional intelligence, and not “fitting in” with their peer group. Paradoxically, they are also intelligent by traditional measurements.
Obsession with weapons: Shooters tend to study how to build explosives, learn how to acquire guns from the high powered assault rifle to glock handgun, and many have collection of weapons like knives as well.
Lack of Ethics: Shooters are resistant to learning and displaying ethical decision making.
No meaningful friends: Shooters tend to remain by themselves, unless they find—perchance a like-minded person like the two shooters in the Columbine shooting.