Jeff Green (8) and the Celtics were up against it Sunday against the Heat as Rajon Rondo was lost for the season. (AP)

Paul Pierce hit the go-ahead jumper with 30.4 seconds left in double-overtime and earned a triple-double with 17 points, 13 rebounds and 10 assists as the Celtics snapped their six-game losing streak with a heart-pounding 100-98 win over the Heat Sunday at TD Garden. It was Boston’s second straight double-overtime game.

LeBron James scored a game-high 34 points and forced overtime with a clutch 3-pointer while Ray Allen had 21 off the bench in his first return to Boston since leaving for Miami as a free agent, and help the Heat rally in the final minute of regulation. The Heat fell to 28-13.

Kevin Garnett scored a team-high 24 points and grabbed 11 rebounds for the Celtics, who could not protect a four-point lead in the final minute of regulation but managed to improve to 21-23 on the season.

The game was played under a cloud for the Celtics, as they found out in the second half that Rajon Rondo tore the ACL in his right knee and was done for the season. Rondo returned in the third quarter and watched the rest of the game from just behind the Celtics bench.

With Courtney Lee starting for Rondo and Jared Sullinger in the starting lineup, the Celtics stayed close in the first quarter, trailing by just four, 26-24, after 12 minutes. The Celtics managed to stay close in the second and forged a 45-45 tie.

WIth news breaking in the third quarter that Rondo had a torn ACL in his right knee and was done for the season, the Celtics managed to put up a fight taking a three-point lead. Garnett’s jumper 16 seconds into the second half gave Boston its first lead since early in the first quarter. Boston built the lead to 60-57 before Miami finished the period on a 11-4 run to take a 68-64 lead into the fourth.

Jeff Green drilled a three from the left baseline to bring the Celtics within one, 72-71, and then after James missed a three, Leandro Barbosa put back a miss to give the Celtics a 73-72 lead with 8:26 left in the fourth. Green’s one-handed slam over Chris Bosh with 7:48 left sent the Garden crowd into a frenzy and put the Celtics up, 75-72.

Pierce drove in for a go-ahead layup with just under six minutes left. Allen connected for a three with 4:38 left to put the Heat up, 78-77, and grabbed a rebound off a Pierce miss moments later. Jason Terry responded with a 15-foot step-back jumper to put Boston back up, 79-78, with just over four minutes left. James responded with a 12-foot fadeaway with three minutes left, putting Miami ahead, 80-79.

Garnett hit a pair of free throws with 2:40 left to put Boston back ahead, 81-80. Allen was fouled by Pierce with 2:19 remaining and Allen converted only one of two for an 81-81 tie. Pierce drove to the basket on a spinning move with 1:59 left to put Boston up, 83-81. After a missed three from Shane Battier, Garnett hit a mid-range jumper with 59.9 seconds left to give the Celtics their biggest lead, 85-81.

Allen drained a three from the left baseline with 25.1 left to cut Boston’s lead to one, 85-84. Wade nearly stole the ball from Jason Terry but was called for the foul. Terry hit both free throws with 21.2 seconds remaining to restore the lead to three points, 87-84. Ray Allen missed a baseline three but Bosh tipped the rebound out to James who collected the ball across half-court and dribbled up to 26-feet and nailed a three with 7.0 seconds left. Pierce drove the length of the court but couldn’t get a shot up. Terry just missed a desperate heave at the buzzer, forcing overtime.

After Miami took a 93-89 lead in overtime, Garnett came back with consecutive baskets, including a game-tying nine-footer with 1:14 left. Neither team could manage good looks in the final minute and Wade missed a desperate three as time expired, as the game went into double-overtime.

The teams battled in double-overtime, with the Celtics held to only a pair of Terry free throws while Bosh went in for a layup. James drove to the basket with 1:02 left in double-overtime and completed a three-point play, putting Miami ahead, 98-95. Terry’s layup with 54.9 seconds cut Miami’s lead to one and Pierce came down and hit a 22-foot pull-up jumper with 30.4 seconds left, giving Boston a 99-98 lead.

James missed a jumper and Pierce grabbed the rebound with 5.6 seconds left. He hit one of two free throws to put Boston up, 100-98. Battier’s three was off target as time expired, allowing the Celtics to hang on.

For complete coverage from Mike Petraglia and Ben Rohrbach, including video, visit the Celtics team page at weei.com/celtics.