At about 3:55 PM on Thursday, December 7, 2017, officers assigned to District B-3 (Mattapan) made an onsite firearm arrest in the area of 89 Tennis Road in Mattapan after responding to assist an officer involved in a foot pursuit. The arrest came after a BPD Captain observed a male suspect, later identified as Brajon Brown, 18, of Mattapan, threatening another male with a long-barreled revolver in front of the Mattapan Branch of the Boston Public Library located at 1350 Blue Hill Avenue. When the captain went to intervene, the suspect fled on foot across Blue Hill Avenue and down Hazelton Street. With the assistance of numerous additional responding officers and several concerned citizens, the suspect was tracked to 89 Tennis Road where he was placed in custody without further incident. Officers then retraced the suspect’s path of flight and safely recovered a loaded .22 caliber Model 686 revolver which the suspect had discarded as he fled. The suspect will appear in Dorchester District Court on numerous charges including Unlawful Possession of a Firearm and Unlawful Possession of Ammunition.