ROXBURY — A late-night street brawl in Roxbury spiraled out of control after a man allegedly pulled out a firearm, triggering a heavy police response as a rowdy crowd tried to interfere with the arrest, authorities said.

Boston police were called to the area of Fountain Street just after 10:20 p.m. Saturday following reports of a fight involving a man with a gun. Witnesses told officers two men had been fighting and that one had brandished a firearm before fleeing the scene.

Officers quickly spotted a suspect matching the description running toward Dabney Street, where he joined a group gathered outside a nearby home. As police moved in to make the arrest, the scene erupted into chaos.

According to police, the suspect resisted arrest and attempted to flee into a building while multiple bystanders tried to physically interfere, grabbing officers and attempting to pull them away in an effort to stop the arrest.

During the struggle, police say the suspect reached toward the front pocket of his sweatshirt, prompting officers to force him to the ground and place him in handcuffs.

A search of the suspect uncovered a loaded Glock 30 S handgun with an obliterated serial number, including one round in the chamber and seven rounds in the magazine, police said.

The suspect was identified as Phillip Anderson, 45, of Roxbury. He was taken into custody and is expected to face multiple charges, including carrying a loaded firearm without a license — a fourth offense — defacing a firearm serial number, resisting arrest, and firearm violations tied to prior convictions.

No injuries were reported.

Police did not say whether additional arrests are expected stemming from the crowd interference, but emphasized the situation escalated rapidly once officers arrived on scene.

The investigation remains ongoing.