A man set himself on fire in a park across the street from the New York City courthouse where former President Donald Trump is on trial.

The man, Maxwell Azzarello, was badly burned and taken to a hospital in critical condition, officials said.

Trump was inside the downtown Manhattan courthouse at the time and was made aware of the fire outside, sources told ABC News.

The NYPD said there were no threats to public safety but the NYPD Bomb Squad was sweeping the area out of an abundance of caution.

Azzarello took pamphlets out of his backpack and threw them around the park before pulling out a canister, pouring a liquid on himself and lighting himself on fire, Jeffrey Maddrey, NYPD's chief of department, said at a news conference.

He eventually fell to the ground and civilians, police and court officers ran into the park to try to extinguish the blaze, Maddrey said.

"He doused himself and threw these pamphlets across the park ... and immediately just lit himself on fire," one witness told ABC News.

The witness said the flames "were just massive immediately."

"Pretty horrific thing to see," he said.

The pamphlets appeared to be "propaganda-based," officials said.

Officials described Azzarello as a "conspiracy theorist."

Azzarello is from St. Augustine, Florida, and arrived in New York earlier in the week, officials said. It appears he acted alone, officials said.

"We’re very concerned," Maddrey said. He said the NYPD will review security protocol because of the "gravity of the event going on," referring to the Trump trial.

Trump is facing felony charges related to a 2016 hush money payment to adult film actress Stormy Daniels. It marks the first time in history that a former U.S. president has been tried on criminal charges.

The trial began on Monday with jury selection. The full jury panel was selected by midday Friday.

Opening statements will take place Monday.

If you are struggling with thoughts of suicide or worried about a friend or loved one, call or text the Suicide & Crisis Lifeline at 988 for free, confidential emotional support 24 hours a day, seven days a week.