Two things you don't see often in this life: Bon vivants who listen to the Cure and middle-aged assassins.
Czolgosz was 28 when he killed President McKinley.
Gavrilo Princip was 19 when he killed Archduke Ferdinand.
Hinckley was 25 when he shot Reagan.
Yigal Amir was 25 when he killed Yitzhak Rabin.
Wilkes Booth was 26 when he killed Lincoln.
Lynette Fromme was 26 when she tried to kill Gerald Ford.
Arthur Bremer was 22 when he shot George Wallace (Travis Bickle was partly modeled on Bremer*).
Sirhan Sirhan was 24 when he killed RFK.
Mehmet Ali Agca was 23 when he shot Pope John Paul II.
Mohammad Bokharaei was all of 17 when he killed Iranian Prime Minister Hassan Ali Mansur.
If Stefan Wisniewski killed Germany's Attorney General Siegfried Buback, he did it the day before his 24th birthday.
Giuseppe Zangara was 32 when he killed Chicago Mayor Anton Cermak while attempting to shoot FDR.
Truman's failed assassins were 36 and 20.
van der Graaf, who was 32 when he killed Pim Fortuyn, was an elder statesman of the assassination racket.
Jean-Marie Bastien-Thiry was also long in the tooth, being almost 35 when he tried killing De Gaulle.
The reason assassins are usually mere babes (particularly when it comes to random "lone gunmen"): is obvious: Young people are romantic, and only a pie-in-the-sky romantic sacrifices himself to commit a murder that in 99% of cases alters very little. If the killing of Franz Ferdinand led the way to WWI, it was the exception.
People in their 40s and 50s might care about politics, but in addition to being less romantic about the world they usually also have more to live for; kids, spouses, mistresses, etc. A 22-year-old guy is living for beer and Transformers 5; hardly impenetrable walls against foolish revolution attempts.
Even when assassinations involve teamwork the organizations behind them normally rely on wide-eyed youngsters to commit the actual violence. The heads of these organizations know it ain't easy getting a boomer to try a low percentage act of terror that will change nothing and end with his facing a firing squad.
When you're young you feel much more strongly about revenge; even if it is macro revenge, the kind you take against political figures. Plus young folks are more likely to harbor a sense of destiny; they compare themselves to Great Ones much more often than oldies. Someone who thinks he's destined for greatness is going to be far more inclined to TAKE ONE FOR HISTORY.
By the time you're older you're more aware that nothing changes. This is why young people, including the non-assassins, do most of the marching and screaming. They're too young to know no one is listening.
*Behind every would-be "great man" is a woman who said no.