WASHINGTON -- The Boston Celtics arrived dressed in black, hoping to bury the Washington Wizards. John Wall would not have it, not on his home-court.

Wall sank a game-winning 3-pointer with 3.5 seconds remaining as the Washington Wizards forced a Game 7 in the Eastern Conference semifinals series against the Boston Celtics with a 92-91 victory Friday.

Wall's heroics came after Al Horford's jumper with 7.7 seconds left put the top-seeded Celtics ahead 91-89.

Washington's Bradley Beal had 33 points and Wall scored 26 despite shooting 9 of 25 from the field. The Wizards won despite coming off a 22-point loss in Wednesday's Game 5 and the fact that the franchise had lost seven straight elimination games at home.

"We just came in with the mindset that we just wanted to play great," Wall said. "Just go out there and compete, give it our all and see what the outcome (is). Come away with a win and forced a Game 7."

Isaiah Thomas scored 27 points for the Celtics but missed a final 3-point attempt at the buzzer. Avery Bradley also scored 27 points and Horford finished with 20.

Monday night's Game 7 in Boston will be Washington's first since 1979. The winner will tip off the Eastern Conference finals Wednesday in Cleveland.

Washington prevailed despite shooting 5 of 24 on 3-pointers. Wall isn't at his best firing from beyond the arc -- and he started the game 1 of 12 from the field. Considering the alternatives, Boston could live with that final attempt -- except for the result.

"He's such a great guy getting to the rim and getting downhill on guys," Boston's Jae Crowder said. "Avery did a heck of a job on (Wall) all night but he has that confidence to take that shot."

Washington shot 43 percent overall. Boston shot 40.5 percent from the field and finished 11 of 35 on 3-pointers.

Thomas scored five straight points to put Boston up 87-82 with 1:34 remaining. Washington countered thanks to its dynamic backcourt. Beal, after missing all seven of his 3-point attempts, drained a shot from beyond the arc and Wall tied the game by hitting two free throws with 41.2 seconds remaining.

Markieff Morris had 16 points and 11 rebounds for Washington. The Wizards' other starting forward, Otto Porter, was scoreless in 36 minutes.

Lopsided results had dominated this first postseason series between Boston and Washington since 1984, with each game decided by at least 10 points. After the Wizards won Games 3 and 4 by 27 and 19 points, respectively, the Celtics roared back with a 123-101 victory in Boston on Wednesday.

In Game 6, the Wizards found some life in a choppy first half, turning a 28-28 tie into a 40-30 lead on Jason Smith's free throw with 3:46 remaining.

Following 3-pointers from Thomas and Horford, Bradley's alley-oop dunk in the closing seconds sent Boston into halftime leading 42-41 despite shooting 35 percent from the field.

Wall continued his trend of slow starts. After missing his first nine shot attempts in Game 4. the four-time All-Star missed 11 of 12 field-goal attempts Friday before hitting three in a row in the third. He scored 13 in the period as Washington entered the fourth trailing 69-66.

Including the regular season, the teams are 10-0 at home in games against each other.

When Washington hosted Boston on Jan. 24, the players dressed in all-black for what they called a "funeral game." The concept came after a matchup earlier in the month at Boston that included a scuffle when Crowder poked Wall in the nose.

Several of the Celtics copied that move ahead of Game 6.

Wall said he found the gesture "funny" when friends told him about the move pregame.

"We knew it was kind of a copycat of what we did," he said. "It was in my mind throughout the game that I didn't want them to come here and basically call it a funeral if we lose at home. We made some big plays. The ball went our way in the end and we get to force a Game 7 in their place."

Bradley said it wasn't planned.

"It was kind of something that just happened," he said.

Based on how these teams have battled all season, Game 7 seemed inevitable.

"Both teams just play really hard," Horford said. "We had some breakdowns here and there that just cost us. It's a learning experience for our group."

NOTES: Game 7 is slated to start at 8 p.m. ET Monday night. ... Washington is 6-0 at home during the playoffs and 5-0 at home against Boston this season. ...Boston F Jae Crowder had 10 points. ...Washington's last victory in Boston came on April 16, 2014. ... The Celtics lost three of four in the head-to-head series with the Cavaliers during the regular season. Washington dropped two of three, but won in Cleveland 127-115 on March 25.