Whackjob

Tom is a whackjob.

Source: tatoeba (3721354)

"He called the guy who owns the gun shop a 'whackjob' and said he's going to take him down if it's the last thing he does."

Source: wiktionary

One of America's most prominent Confederistas is Michael Hill, head whackjob at the looney League of the South—an obscure organization that has already declared southern cultural independence.

Source: wiktionary

2004: Mark. St. Amant, Committed: Confessions of a Fantasy Football Junkie Ronald Reagan took his oath as the fortieth president in American history and, three months later, took a bullet from some wackjob trying to impress the future star of The Silence of the Lambs.

Source: wiktionary