While Janoris Jenkins was causing his own problems during and after the Giants’ most embarrassing loss of the season, a fan of the cornerback became a terror in the stands Sunday.

Video emerged after the game of a fan, wearing a white Jenkins jersey, being ejected from Levi’s Stadium in the fourth quarter of the Giants’ 31-21 defeat by the previously winless 49ers after causing a violent scene in the stands, requiring seven officers to detain and remove him.

Sitting right behind the Giants’ bench with a small New York contingent, the unruly fan began cursing at and showing the middle finger to Giants defenders as they walked back to the sideline following the 49ers’ final touchdown, which sealed their first victory — and the Giants’ eighth loss. Footage shows the fan fighting back against the police officers, who first attempted to escort him from his seat.

The abrasive fan was “heckling” and “tried to spit on” the closest guard, a witness told NJ.com after the game, which led to him tumbling over the wall and onto the field as the guard jumped on top of him and threw a couple of punches. He was met by two more guards who pinned him to the turf, tased and handcuffed him, before leading him out of the stadium along with his female companion.

The incident left the fan with blood on both sides of his face and one guard with a bloody nose, according to the same witness.

Jenkins, in the second year of a five-year, $62.5 million deal with the Giants, showed a lack of energy — and remorse — in his first game back from suspension, failing to stop two long 49ers touchdown plays before blowing off reporters after the loss.