A mask-wearing man who allegedly assaulted another man at an MBTA station in Boston has been arrested.

Transit police say the assault happened at about 7 a.m. on Wednesday at the Green Street Station in Jamaica Plain soon after the 31-year-old victim first encountered the alleged assailant.

The victim told officials that an unknown man put on a face mask and glared at him before entering the station. The two men exchanged words following the glare before the victim went to the inbound platform to wait for a train.

The assailant, who was later identified as 30-year-old David Joress of Brighton, then allegedly hit the victim on the side of the head, knocking him down 5 feet into the right of way area.

Officials say the victim claimed he was temporarily unconscious after the assault. He was taken to a local hospital for an evaluation.

Joress was arrested. It is unclear when he'll be arraigned or if he has an attorney.