BOSTON -- Grant Williams had never taken more than eight 3-pointers in a game before this series. He'd never made more than six. He'd never led the Boston Celtics in scoring. All of those things changed Sunday in the NBA playoffs.

"Grant won us a playoff game tonight," Jayson Tatum said. "A Game 7."

Williams had a career-high 27 points, while Tatum had 23 of his own as the Celtics dominated the second half in a 109-81 victory over the Milwaukee Bucks at TD Garden on Sunday.

Boston needed to win Games 6 and 7 after blowing a 14-point fourth-quarter lead in Game 5 that allowed the Bucks to take a 3-2 lead. But after pulling away late against Milwaukee in Game 6, the Celtics used the 3-point shot to put distance between themselves and the Bucks in Game 7.

The Celtics hit a new playoff franchise record with 22 3-pointers, and Williams tied the NBA record for most 3s in a Game 7 with seven, tying him with Stephen Curry (twice) and Marcus Morris.

Williams' previous career high for 3-point attempts in a game was nine -- which he set in Game 2 of this series. He doubled that mark with 18 3-point attempts in Game 7, breaking the NBA's Game 7 record for attempts, held by Curry.

And it earned him a new nickname in the process, from Jaylen Brown.

"Call him Grant Curry now," Brown said.

The Bucks' defense aims to protect the paint and force other teams to hit 3-pointers. In Game 7, the strategy was to leave Williams open. Bucks center Brook Lopez, who drew the Williams assignment early, left Williams on the wing to take away any drives that Brown and Tatum wanted.

"That's what they were giving us," Brown said. "So we had to keep making the pass, and he was wide open. We trust all our guys, and Grant is a good shooter. And he came through."

Williams hit his first 3-pointer to open the game but missed five of his next six attempts. But his team and his coaches kept telling him that he needed to shoot it if he was open.

"I told him let it fly," Celtics coach Ime Udoka said. "They are disrespecting you more tonight than they were earlier in the series. That was their plan on him and other guys, really shifting and making them try to beat us. You saw it on the first one he made.

"I basically said shoot the ball. What else can you do? Stop driving into the crowd. Shoot the shot that they are giving you."

After passing up a few open shots in the second quarter, their words started to stick.

"It's tough to get into your head when your entire team, like 15 people, walk up to you and say keep shooting," Williams said. "It was just like, they are encouraging it so it was like, might as well take advantage of each one."

Williams didn't enter the NBA as a 3-point shooter. In fact, he made only 15 3s during his final season at Tennessee and only 30 in his career as a Volunteer.

He shot 25% as a rookie from 3 but improved that to 37.2% last season. This year, he upped both his volume and his percentage as he nailed 41.1% while shooting 3.4 per game.

But against the Bucks, Williams had struggled since his Game 2 performance, going just 2-of-14 from deep in his past four games.

That's why Milwaukee decided to leave him open in Game 7. Unfortunately for the Bucks, that strategy backfired.

"He came up big," Tatum said. "He played amazing. In the playoffs, you need that. You need guys coming off the bench to be a star in their role."

Boston finished the game shooting 22-of-54 from 3-point range, while the Bucks struggled mightily, going just 4-of-32.

According to ESPN Stats & Information research, that's the largest 3-point differential in a Game 7 in NBA history and tied for the largest 3-point differential in any playoff game (Golden State had 21 to Oklahoma City's 3 in Game 6 of the 2016 Western Conference finals).

For the series, Boston made 110 3-pointers -- third most in a playoff series all time -- to just 57 for Milwaukee. That's also the largest 3-point differential in a series between two teams in NBA history, according to ESPN Stats & Information.

Despite the 3-point shooting, Williams might have outwardly shown the most emotion of the night on a defensive play in the fourth quarter with the game practically in hand.

With Boston up 94-73 midway through the final period, Milwaukee's Bobby Portis got the ball in the open court and the only obstacle between him and the rim was Williams. Portis went up for a dunk, and Williams swatted it away.

Williams turned around and pumped his fist at the crowd as the TD Garden erupted.

"When I got the block, I was just super excited and really, really pumped," Williams said. "Because over the years of your career, you'll have moments where it goes the other way and you'll have ones where you get the block."

Sunday's win also marked the first time the Celtics had overcome a 3-2 deficit to win a series since the 1988 Eastern Conference semifinals against the Atlanta Hawks. That year, the Celtics dropped the Eastern Conference finals to the Detroit Pistons, a fate they are looking to change this year.

This is Boston's fourth trip to the Eastern Conference finals in the past six seasons. The previous three -- including 2020 in the Orlando, Florida, bubble against the Miami Heat -- have ended in defeat.

Brown was on the previous three teams, and he knows the hard work isn't over.

"We still got a long journey ahead," Brown said. "Whatever you gotta do to get your mind right, your body right, get ready to go. No excuses."

Game 1 of the Eastern Conference finals is Tuesday in Miami. Whether Williams attempts 18 3s again shouldn't be up for debate. Before he went on to praise Williams, Tatum had a message for the third-year forward from Tennessee.

"I told him don't get used to that," Tatum said.

What Boston can get used to, however, is more playoff basketball.