ROXBURY — Fifty people. A bank. A gun. And a foot chase through a shoe store parking lot in broad daylight.

Officers received the call around 4:28 p.m.: approximately 50 people fighting outside a bank near 2343 Washington Street. A male had been seen brandishing a firearm during the melee.

Fifty people. In the middle of the afternoon. Outside a bank. With a gun in the mix.

Officers scrambled to the scene and got a description of the armed suspect and his direction of flight. He was heading toward the Bruce C. Bolling Municipal Building in Nubian Square — the city government building directly across the street from the brawl.

Police tracked him to the rear parking lot of a shoe store at 2275 Washington Street, where they spotted a man matching the description approaching a group of people.

When officers stepped out of their cruiser, he ran.

They chased him through the parking lot and tackled him. He resisted arrest but was cuffed without further incident.

Then they searched his backpack.

Inside: a black HK VP9 semi-automatic pistol with a light attachment, loaded with a 17-round magazine containing eight rounds of 9mm ammunition. Two additional loaded magazines — one with nine rounds, the other with nine more. And a plastic bag with 13 loose rounds rattling around at the bottom.

Thirty-nine rounds of ammunition. In a backpack. At a 50-person street fight outside a bank.

Kareem Samir Williams, 37, of Boston, was arrested and charged with carrying a firearm without a license, carrying a loaded firearm without a license, possession of ammunition without an FID card, and possession of a large capacity feeding device.

He is expected to be arraigned at Roxbury District Court.