The Hawks' defense staggered the Pacers with some late stops.
Now Atlanta is heading home with a chance to deliver the knockout punch to the Eastern Conference's top seed.
Scott scored all 17 of his points during the Hawks' incredible second-quarter run, and the defense fended off the Pacers' frantic fourth-quarter charge to hold on for a 107-97 victory and a stunning 3-2 lead in the first-round series.
"We can play with this team," Scott said. "They're a great team, especially at home, great players, great coach, but we have a belief in ourselves as well."
All the Hawks have to do is protect their home court and they will reach the second round for the first time since 2011, and throw the East into disarray after the talk all season was about an Indiana-Miami rematch in the conference finals.
That looks like a long shot now. The Pacers haven't won back-to-back games with their regular starters in the lineup since mid-March and the league's best regular-season home team (35-6) has inexplicably given away home court advantage to the Hawks -- twice.
They're making it look easy, too.
Atlanta shredded one of the league's top defenses during a remarkable second quarter, making 13 of 16 shots overall and 9 of 11 from beyond the arc. Scott made all five of his 3s during the decisive 30-6 run, which actually started with the final basket of the first quarter, to turn a 21-18 deficit into a 48-27 lead.
Indiana never recovered.
Atlanta outscored the Pacers 41-19 during that 12-minute stretch, matching the second-highest second-quarter scoring total in the franchise's postseason history. The Hawks scored 41 against Detroit on March 17, 1986, and the St. Louis Hawks had 45 against Fort Wayne on March 14, 1957.
Indiana, meanwhile, allowed a second-quarter franchise record, breaking the previous mark of 39 points set by Boston on April 23, 2005.
The Hawks joined the 1970 Milwaukee Bucks as the only road teams in the shot-clock era to score at least 40 points in a quarter and give up fewer than 19.
Not enough? Atlanta tied an NBA record with 9 3-pointers, most recently done in 2008, and also broke the franchise playoff record for 3s in a game with 15. The previous mark was 12.
"I didn't even know," Kyle Korver said after making two 3s in the second quarter and another late in the game to keep the Hawks in control. "Mike got hot. I don't know how many 3s he hit in that quarter. Mike hadn't shot the ball as well as he did tonight, but he hasn't shot that well all series."
The Pacers, meanwhile, endured yet another bleak chapter in a second-half collapse that could go down as the worst in NBA history -- if they lose either of the next two games.
And it was downright dismal.
Roy Hibbert finished without a point or a rebound for the first time in his playoff career. Indiana was outrebounded for the first time in the series and its rebuilt bench was outscored 45-23.
Paul George led the Pacers with 26 points and 12 rebounds. George Hill, Lance Stephenson and David West all had 16 points, not quite enough to rally on a night they were again serenaded with boos in the first half.
"It was frustrating because we didn't make a change," George said of the Pacers' defense. "We let them run the same action, the same shot. We didn't do nothing. So that was frustrating."
The game changed in a hurry.
Atlanta opened the second quarter with a free throw from Mack to tie the score at 21. Scott then made four consecutive 3s to push the lead to 33-21. Mack followed that with a midrange jumper, Korver made a 3, Scott scored on a putback and Korver hit his second 3. Mack followed that with two free throws and Scott closed the run with his last 3 of the game to make it 48-27.
The Pacers still trailed 61-40 at halftime and by as many as 30 points in the third quarter before the frantic comeback.
Indiana cut the deficit to 85-67 late in the third and with the crowd urging them on, the Pacers made it 96-87 on C.J. Watson's layup with 4:04 to go.
But Korver answered with a 3 and the Hawks closed it out at the free-throw line.
"We don't do much for moral victories, we just dropped the ball," West said. "Everybody's got to be ready to play and I didn't think we responded well enough."
The Pacers had a moment of silence to honor former coach Jack Ramsay, who died Monday at age 89. Ramsay led the Pacers to the first NBA playoff win in franchise history. ... Atlanta has three wins at Bankers Life Fieldhouse and is the only team to beat Indiana on its home court more than once this season. ... The Pacers are 0-10 in series when trailing 3-2.