Many mass shooters have had unique situations and agendas, in most cases mass killers have displayed signs of isolation and separation from society and for unknown reasons a sense of betrayal from society so there are definitely certain signs that cause concern.

There have been many instances where mass shooters who have had premeditated attacks had planned the attack months or days ahead,  of course there is no way an average person can determine  for certain the mind of a criminal, but when a person who seems suspicious by displaying signs of withdrawal from society,  such as having feelings of bitter resentment towards certain public issues, or being easily irritated by minor things, when such people make a purchase of multiple rounds of fire arms red flags should be raised just as a bank would get suspicious about an individual who for years has been depositing one thousand dollars a month, suddenly deposits one hundred thousand dollars and report it.

However this does not in any way imply that everyone who displays signs of isolation, or resentment towards society may become a mass murderer in any way, as there are plenty of people who display these signs and may even make provocative statements that may seem disturbing to others, but would never dream of resorting to criminal actions.

So how does one determine a potential criminal and act upon it? Even though there may be no clear cut answer looking out for a combination of signs might help, such as raising an alarm when an individual who displays signs of bitter resentment towards society also displays a good knowledge of guns or explosives. Such individuals should be engaged by counseling and care.