BOSTON -- Point guard Isaiah Thomas scored a team-high 33 points Sunday in Game 1 of the Boston Celtics' first-round playoff matchup with the Chicago Bulls, one day after the death of his sister in a one-car crash.

Thomas, overcome with emotions multiple times before the start of the game, finished on 10-of-18 shooting with six assists and five rebounds over 38 minutes.

The Bulls emerged with a 106-102 triumph and lead the series 1-0. Game 2 is Tuesday night at TD Garden.

Celtics coach Brad Stevens said Thomas was "struggling'' prior to the game, and it showed early, as he uncharacteristically missed his first free throw attempt short off the front rim.

How he was able to lock in down the stretch was no surprise to his coach.

"[Thomas] was incredible," Stevens said. "He's an amazing, amazing player. Amazing person. ... I couldn't help but be inspired by his play."

The Celtics held a pregame moment of silence for Chyna Thomas, who died early Saturday in a one-car interstate accident in their home state of Washington. She was 22. Thomas was informed of her death following the team's practice Saturday afternoon.

It was unclear if he'd play Sunday, and prior to the game, television cameras captured teammate Avery Bradley comforting Thomas on the bench during the pregame shootaround. But Thomas led the team onto the floor and got a huge ovation from the Boston crowd. He was the last of the Celtics' starters to be introduced and was immediately surrounded by his teammates. He bowed his head throughout the tribute, and tears dripped down his cheek.

On his sneakers were written several messages, including "Chyna," "R.I.P. Lil Sis" and "I love you."

Thomas did not address the media afterward, but his teammates said he was emotional throughout the day.

"It says a lot. Isaiah, to me, is like family,'' Bradley said. "We grew up in the same area. I know it's tough for him. It says a lot about him. He's a true competitor, and tonight he was playing for his sister, and he was playing for his family.''

Celtics big man Al Horford acknowledged afterward that emotions were tough for not just Thomas but also the entire team.

"We're never going to make excuses, but this is hard,'' Horford said. "This was difficult, and I felt like our guys really dealt with it best. We knew [Thomas] was hurting ... we have a lot of respect for him that he was able to come out.''

Stevens said he remains open to whatever Thomas needs to do moving forward, including allowing him to return to Washington if he needs to be with his family.

"Whatever he needs to do, he needs to do, and we'll help him in any way," Stevens said.

Before the game, Stevens said the decision about whether the All-Star guard would play was up to Thomas, adding that "he's really hurting" after his sister's death.

"We've talked, a little bit last night and then again today, about as he goes through it, and if he feels like he needs to not [play], then whatever he wants," Stevens said. "I think that one of the things that I've learned, having been through situations in the past, is that there's really no right or wrong answer. It's whatever's right for him. That's what we've encouraged him. And he's really hurting. It's a tough situation."

Stevens fielded five questions during his pregame news conference, and all five were related to Thomas. Stevens said the Celtics have done all they can to console Thomas.

"It's whatever's right for him," Brad Stevens said pregame of whether Isaiah Thomas would play Sunday in Game 1. "That's what we've encouraged him. And he's really hurting. It's a tough situation." David Butler II/USA TODAY Sports

"I think everybody reached out. It's a close-knit team. He's a big part of it," Stevens said. "Isaiah's a great teammate. Isaiah's a great husband. He's a great father. He's a great guy, great son and brother. And I think, ultimately, we just all tried to do our part in letting him know we were thinking about him, and anything we could all do to help, we'd do. That family and this particular situation with his family takes precedent over everything else going on. And that we're here for him if he needs us."

Added Stevens: "I don't think there's any question that people around here have a great affinity for him. And we've all, even in my short time here, when you see that really tough things happen to people, this [Boston] community really rallies around them. So you can already feel that. You can already feel, as I was at church this morning, I could feel people coming up to me, and they all wanted to know how he was doing and all talking about it. When you get here, that's all everybody wants to talk about. I think it's going to be really emotional. And that's part of what makes this place really special is they get it. I think they really appreciate Isaiah, and I know Isaiah really appreciates everybody here."

Stevens said his team was ready for Game 1 after three days of preparation, and he said they would balance supporting Thomas with competing on the court.

"Part of being supportive for him is putting our best foot forward," Stevens said. "And letting him know it's OK, whatever his emotions are at that time, it's OK to let them out. Again, and you all know this from having really tough stuff happen: I don't know that there's a script for this. I don't know that there is a script for the emotions that somebody is supposed to show. I think that, ultimately, however you feel, that's the way you feel. And I think that we're here, again, as a support. And part of our support is to be great teammates, and great teammates are ready to compete together and compete for each other."

Inside the Celtics' locker room, Gerald Green fought back emotions while trying to put into words what Thomas is going through.

"I'm playing this postseason for him," said Green, who signed with the Celtics last summer in large part because of his relationship with Thomas. The two played together previously in Phoenix.

Added Green: "I can't really explain how tough this is right now, man."

Horford said prior to Sunday's game that Thomas has encouraged the team to focus on the postseason, and the players were trying to honor that heading into Game 1.

"It has to be,'' Horford said. "Isaiah is a very strong man, and none of us have any idea what he's going through or feeling. The fact that he's even here is just a lot of credit to him. It's a difficult time, but we're here for him, and we're going to go out and compete and play hard.''

Forward Tyler Zeller said the Celtics want to try to make Thomas' basketball world as easy as possible right now.

"He's the reason we are where we are,'' Zeller said. "He's had an unbelievable season, and he's our No. 1. ... We're gonna go out and help him out in any way.''

The Bulls were among the first NBA teams to release a statement of condolence for Thomas on Saturday. Chicago coach Fred Hoiberg said he expected what is usually a high-energy Boston arena to be filled with even more emotion Sunday.

"It's a horrible tragedy,'' Hoiberg said. "He just seems like such a good kid, and obviously, he's one of the great competitors we have in our league. ... It's just awful what happened.''

Jimmy Butler, who played alongside Thomas on the past two Eastern Conference All-Star teams, said he also was in awe of what Thomas was able to do.

"He's a helluva player,'' Butler said. "It just goes to show the type of player and man he is to go out there and battle through what he was going through for his organization and team.''

Golden State star Kevin Durant talked about Thomas after the Warriors' Game 1 victory over Portland on Sunday.

"We're all praying for him," Durant said. "The NBA family's behind him."

The Associated Press contributed to this report.