John Giamella, a 19-year-old from Staten Island, was arrested on Friday and charged with harassment after allegedly threatening the life of Knicks owner James Dolan on Twitter, according to multiple reports.
"James Dolan, it's officially time to die," Giamella allegedly tweeted.
Police said that was followed by a tweet that read "Death to James Dolan."
Giamella, the son of a New York City cop, also reportedly posted photos of himself naked while holding a gun and another of him holding a sharp metal object to his neck, according to the New York Daily News.
The head of security at Madison Square Garden contacted police after becoming aware of the threats, the spokesman said.
Dolan, 58, is the chairman of Madison Square Garden and owner of the New York Rangers. He's also the son of Charles Dolan, the founder of the cable TV company Cablevision, which the Dolan family continues to own. The Knicks are currently 21-35 and have only one playoff series win since 2000. The Rangers are 32-24-3 but haven't won a Stanley Cup since 1994.