Police say 28-year-old Kylike Fischer is charged with criminal mischief.
Officials tell The Trentonian the damage was done around noon Sunday.
An official with the Trenton Firemen's Benevolent Association says a witness told a security guard, who told police.
The statue is more than a century old and memorializes firefighters who died in the line of duty.
It's been moved to the Trenton Fire Department's museum so it will not be damaged further.
Information from: The (Trenton, N.J.) Trentonian, http://www.trentonian.com