The man reportedly approached fans and said that the IRS "ruined his life." He shouted about peppermint tea and tried to get bystanders to read a pile of documents before throwing them and threatening to cut himself.
He produced a pocket knife and used the blade to hack his wrists. He was wrestled to the ground, but produced a second knife to cut the other wrist.
A widely circulated amateur video captured by an apparent bystander, identified as @SirAnduck, shows the man being tackled by police on the plaza.
NYPD and plaza security restrained him while waiting for emergency medical personnel. The man, who is in his fifties, is expected to recover.
Fans and tourists were shocked by the scene, saying there was blood everywhere. An outside segment was cancelled due to the incident, and security cleared the plaza as custodial crews powdered and mopped the blood and gore.
About an hour later host Matt Lauer tweeted, "All secure on the plaza after a scary incident. Thanks to our security team and the NYPD."