You will notice all these men have at least two things in common, their young age and the fact that they are linked to one horrific event.
James Holmes, 24, is said to be involved in the Colorado movie theater massacre, Adam Lanza, 20, Sandy Hook Elementary shooting, and Dzhokhar Tsarnaev and his brother Tamberlan, 19 and 26, are accused of the Boston Bombings.
Thomas Cory, a psychologist, says, "There's some evidence that if you're going to develop a mental disorder, an extreme mental disorder, it tends to occur quite often in males late adolescence, early adult hood."
That led us to ask the question why.
Cory adds, "It seems to be a mix of cultural and biochemical events, social events.
John Lee, a therapist who specializes in children and adolescents, also weighs in on why young men are said to have committed these crimes, rather than women or older men.
Lee says, "I think young people can often be swayed in the wrong direction too. You see this commonly in gangs, in sometimes extreme situations."
With this latest incident in Boston, these men say Dzhokhar could have worshipped his brother.
Cory adds, "He possibly got involved in a very radical form of Islam, radical, not normal."
And while Dzhokhar did not fit the so-called mold of a killer, experts say his brother threw up a couple disconcerting red flags.
Cory adds, "The assault is worrisome. The boxing itself, no."
Now, a lot of professionals agree, more research needs to be done on mental health, so these patterns can be figured out.