Cops busted a third suspect in connection with a vicious attack on a 79-year-old man who attempted to break up an apparent play fight between two teens in Queens, police said Friday.

The third suspect –– a 14-year-old boy who was not named because he is a juvenile –– was busted Thursday afternoon and is facing a count of gang assault and disorderly conduct, police said.

The teen surrendered to the detective squad in the 105th Precinct in Queens Village, according to police sources.

The assault, which happened shortly before 11 a.m. Tuesday, Oct. 8, in front of the Cambria Heights Public Library on Linden Avenue, left the elderly man with a broken femur and ribs after he tried to break up the fisticuffs.

The boys –– 18-year-old Nyziere Lodge and an unidentified 15-year-old –– began chasing the man down the sidewalk, according to disturbing video released by police.

One of the teens pushed the man to the ground while the other repeatedly punched him in the face and chest, according to the police and video footage.

The attackers fled, and the victim was taken to Long Island Jewish Valley Stream Hospital, cops said.

The pair were busted on gang assault charges earlier this week.