Boston, MA (AP)  -- Kevin Garnett took a behind-the-back pass from Paul Pierce, slammed in the dunk to make the lead three dozen points and then slashed his hand across his throat to signal what the Atlanta Hawks already knew.

"It's over," he told the crowd.

The game. The series. The surprising little scare Atlanta put into the NBA's best.

Garnett had 18 points and 11 rebounds, Pierce scored 22 points, and the Celtics turned back the pesky Hawks with a 99-65 victory Sunday in Game 7 of their playoff series to advance to the second round.

Next up: LeBron James and the Cleveland Cavaliers. Game 1 is Tuesday night.

"They're a group that's defending Eastern Conference champs," Garnett said. "To do anything, you've got to go through them. "It's good that we have home-court advantage. I think it should be a good series."

The Celtics started the celebration early, holding the Hawks to 10 points in the second quarter and doubling their 18-point halftime lead in the third.

The fans yelled "We want Cleveland!"

The public address announcer explained how to buy tickets for the second round.

And, in the background, the new Boston Garden shook with Gladys Knight and the Pips singing that the Hawks were "Leaving on a Midnight Train" to Georgia.

"I wish we could have played all of our games in Atlanta," said coach Mike Woodson, whose team won all three home games but never came close to stealing one in Boston. "Nobody thought we had an opportunity to even win a game in this series. We battled them right to the end. We just didn't have it today."

Rajon Rondo, who missed a potential game-tying 3-pointer in the Game 6 loss that forced the series back to Boston, had 10 points and six assists, taking his lumps on a key play. Kendrick Perkins had 10 points and 10 rebounds before joining the rest of the starters on the bench in the formality of a fourth quarter, just like the Celtics did for much of the regular season.

Boston went 66-16 for the league's best record -- 29 games better than the young Hawks team that earned the last playoff spot in the Eastern Conference. The home-court advantage proved pivotal against an upstart team that fed off its own crowd but wilted on the road, losing four times by a total of 101 points.

"I really had no doubt in my mind how we were going to come out," Pierce said. "You kind of saw it from the guys after Game 6 on the plane, there wasn't a lot of talking. We knew that we let a couple of games get away in Atlanta and I knew we were just going to take care of business."

The skirmishes of the first six games boiled over with 9:09 left in the third quarter, with Boston already leading 51-28, when Rondo got the ball on a breakaway in the third quarter and had only Marvin Williams to beat.

The Hawks forward put an arm across his chest and took Rondo to the floor, where he lay for a few minutes while Celtics coaches and teammates checked on him. The officials immediately signaled a Flagrant 2 foul and, after reviewing the play, threw Williams out of the game.

"I saw it on TV and it did look pretty bad, so I can't argue that at all. I just want Rondo to know that I would never try to hurt him," said Williams, who called Rondo a friend since high school. "He knows the type of person I am. ... It was a physical series, but I have no bad blood with Rondo."

Boston coach Doc Rivers also vouched for Williams. "Two good kids playing hard," he said.

Woodson said it was just the latest in a series full of hard fouls, but he conceded that making the Celtics angry probably wasn't the best approach.

"This series has been so hard-fought, guys' bodies all over the floor," the Hawks coach said. "It probably did energize them some. But I don't think that was the difference in the ballgame. We struggled right from the start."

Rondo hit both free throws, the Celtics got the ball and Ray Allen, who hadn't made a basket since the first quarter, drained a 3-pointer to make it a 28-point game.

Then came showtime.

The Celtics brought out some fakes and behind-the-back passes straight out of the Harlem Globetrotters. Rondo found Garnett underneath for an emphatic dunk -- and the menacing gesture that will surely earn Garnett a fine from the league office -- with 3:05 left in the third.

A minute later, he got his payback, knocking Zaza Pachulia to the floor on a backcourt pick. Rivers, who earned his first playoff series coaching victory, took Garnett out of the game; he wasn't needed.

With 10:44 left in the game, Pierce and Rondo joined him on the bench. Pierce, who was fined for what the league called a "menacing gesture" in Game 3, was the only Celtics starter to play more than 30 minutes. Sub Leon Powe was the third-leading scorer, with 12 points and four rebounds in 20 minutes.

Notes:@ Williams, who was sore from a knee-on-knee collision with Pierce in Game 6, started. ... The Celtics are 18-5 in Game 7s, but they had not won one since beating Atlanta in the second round in 1988. Counting best-of-five and best-of-three series, Boston is 23-8 in deciding games. The Hawks franchise is 2-8 in seventh games and had not won one since 1961. They are 8-14 in decisive games overall. ... Allen was 2-for-11 in the first half, missing all four 3-pointers he tried. ... Atlanta scored 26 points in the first half, a record low for a Celtics opponent.