The center's general manager, Lee Zeidman, said the man, who was not identified, walked into the venue through an employee entrance. He said security officers tried to block his entry, but the man was brandishing the blade.
The man ran to the arena floor, where he was met by 25 security staffers who surrounded him until police arrived.
He eventually made his way to the visiting bench, where he spoke to three police officers with their guns drawn from approximately 20 feet away.
Zeidman said the man made no demands or offer a motive for his actions.
"He was talking a lot of gibberish, making a lot of veiled threats, and nobody could really understand him," Zeidman said. "There were no specific demands. He told us: 'Just back away or else you're going to get hurt. Leave me alone. I'm prepared to do whatever it takes to get whatever I want."'
Police shot the man with a beanbag gun and detained him after he made a move toward a tunnel leading off the court. He was placed in handcuffs and escorted out by police.
Spectators with VIP access to the 12:30 p.m. game had begun filing into the arena, but were evacuated once the incident began. Players from both teams watched the drama unfold on a TV outside the Cavaliers' dressing room before they were instructed to return to their locker rooms.
The court was reopened to players, media and arena employees 18 minutes after the man's arrest.
Officer Norma Eisenman, a police spokeswoman, confirmed the man's arrest and said an off-duty officer reported the incident, but did not release other details.
