The man accused of starting a massive fire Monday at the Kings Plaza mall has confessed to the crime, investigators say.

They say 23-year-old Evon Stephens admitted to setting fire to cars at the shopping center's parking garage, and then apologized.

Stephens faced a judge in Brooklyn federal court on Tuesday. Prosecutors say he maliciously used fire to damage and destroy vehicles and personal property.

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A law enforcement source tells News 12 that Stephens is being charged with federal arson because the crime involved property that moves in interstate commerce. That means the cars set ablaze were produced in another state and move around, giving the crime federal jurisdiction.

Investigators say Stephens admitted that he knew he was being recorded on surveillance cameras and that he said he was motivated to start the fire because he believed people were using the parked cars for sexual activity.

The prosecution says the cars were the property of various auto dealerships, including Mercedes-Benz and Jeep, which used the parking garage attached to the mall to store vehicles for sale.

According to the criminal complaint, more than 135 cars in total were damaged. First responders say the fire injured about 20 firefighters and six other people who suffered smoke inhalation and heat exhaustion.

Stephens' lawyer did not have a bail package ready but will have the opportunity to request bail the next time Stephens faces a federal judge.

The mall remained closed on Tuesday but said on Twitter that it would resume normal business hours on Wednesday.

The Department of Buildings says there are no structural stability concerns with the garage, but a vacate order has been issued for the part of it affected by the fire.