"We were able to extinguish the fire and from that point we removed him to Cornell Burn Unit where right now he's there in critical condition," the official said during a press conference.
Another New York Police Department official identified the man who set himself on fire as Maxwell Azzarello from the state of Florida.
Police said Azzarello threw pamphlets on the ground before he set himself on fire.
"The pamphlet seems to be propaganda based, almost like a conspiracy theory type of pamphlet - some information in regards to Ponzi schemes, and the fact that some of our local educational institutes are fronts for the mob," a police investigator said.
Police said Azzarello did not breach any security measures on site for Trump's trial because the incident took place at a nearby park open to the public at the moment.