The Pacers staged a big late rally in regulation, and the Celtics became the first team in NBA playoff history to go scoreless in an overtime.
Boston, which entered Game Five with a 3-1 lead in the best-of-seven series, had an 86-81 lead with 4:27 remaining in regulation, but scored only two points thereafter as both teams struggled offensively down the stretch.
The Celtics forced overtime on a layup by Antoine Walker with 2:01 remaining, but did not score in the final seven minutes.
In overtime, Boston missed all six shots, and Walker misfired on a pair of free throws with 1:58 remaining. The Celtics became the ninth team in league history to go scoreless in an overtime, and first since Dec. 1, 2000. "It almost seemed like the first team to score would win,"
"It was an unbelievable game with unbelievable energy from both teams," said Indiana guard Reggie Miller. "The intensity level was so thick out there. It was a fun game to be a part of."
Boston held the previous record for fewest points in overtime, managing just one in the second OT of a home loss to Charlotte on May 1, 1993.
"Both teams had trouble scoring," Walker said. "I missed two free throws that could've sealed it. It was a defensive battle in overtime."
"They defended well and took us out of our offense," said Boston guard Paul Pierce. "We couldn't get a bucket late in the fourth and in overtime, and you have to give them credit. They were fighting for their lives."
The Pacers snapped a six-minute scoring drought when Artest made 1-of-2 free throws for an 89-88 lead with 68 seconds left. After Boston's Walter McCarty missed a jumper, O'Neal buried a shot from the right baseline with 32 seconds to go.
Pierce fired an airball on the Celtics' next possession, and Artest, who had 26 points and 10 rebounds, sank two free throws with 12 seconds remaining as the Pacers pulled within 3-2 in the Eastern Conference first-round series.
O'Neal collected 19 points and 22 rebounds, and Ron Mercer and Tim Hardaway added 13 points apiece for Indiana.