The man who slashed a 71-year-old woman’s face on a Manhattan subway train Monday was arrested after his girlfriend’s grandmother recognized his distinctive clothing from surveillance video and called police.

Damon Knowles, 21, was picked up Tuesday after he went to his girlfriend’s apartment in Brownsville and started to get violent with her, police sources said.

The woman’s grandmother then recognized the bright red hoodie, black jacket and red sweatpants Knowles was wearing from the surveillance video police had released following Monday’s slashing and called police.

Knowles was taken into custody and charged with assault with intent to cause disfigurement and assault with intent to cause serious physical injury. He was also slapped with trespassing for entering the grandmother’s home.

He was being processed in Brooklyn for the trespassing charge and was to be brought to Manhattan, where he was to be arraigned for the slashing attack.

In that incident, Knowles left a 4-inch gash on a 71-year-old woman’s face when he slashed her while riding a D train near the East Village.