Authorities arrested the arsonist who set Macy’s merchandise on fire inside the dressing room of the Staten Island mall store after he returned to the location on Friday morning, police said.

Brian Pierre, 22, was charged with arson, burglary, criminal mischief and petit larceny for Saturday’s arson — when he allegedly lit $200 worth of store products on fire inside a men’s changing room.

He was also hit with a criminal trespass charge for returning to the location around 7:30 a.m. Friday, police and FDNY officials said.

Pierre’s mother, Irene Torres, took to Facebook earlier this week to explain that her son has suffered from mental illness for three years and needs help.