BOSTON – Antoine Walker’s nightmare series turned worse last night when he left the bench late in the fourth quarter to charge after a heckler in the front row at FleetCenter.

Walker appeared to get right up in the guy’s face but it was unclear if Walker’s left hand made any contact with him. Walker immediately was restrained by security and Celtics personnel before he could get to the fan.

Moments after Walker rushed him, four of Walker’s friends stormed over to the area but couldn’t find the departing fan.

According to eyewitnesses, when Walker came out of the Celtics’ 94-76 loss with 4:42 left and Boston trailing by 22, the fan shouted, “[Richard] Jefferson ate you for lunch!”

Walker got up from the end of the bench and responded by saying,”What did you say to me?” then walked a few steps toward the front row. Walker scored 15 points on 6-of-17 shooting. He’s scored 36 points in the series’ three games, shooting 15-for-52.

According to eyewitnesses, the heckler yelled, “Bring in a sub for Walker!” across much of the contest.

Walker was seen pointing to his friends, who then responded. Afterward, Walker said he was “out of character” but said he had become frustrated by this particular fan across his Boston career.

The fan was ejected from the arena and his season tickets were revoked, the Celtics said after the game.

“It was out of character . . . that fan has been on me for seven years,” Walker said. “It’s the second round of the playoffs. I’ve always seen this guy out in public. The fans have been great to me. I was out of character.

“He never says anything nice to me,” Walker added. “And he continues to badger the team. Guys like that shouldn’t be allowed in the building. There’s a lot of great fans here. I was out of character. I felt bad about it, but in the heat of the game, when you’re giving 100 percent, I’ve been here seven years, he’s always had something to say and I’ve gotten tired of it. I just told him, ‘Don’t speak to me no more.’ “