WALTHAM — If the Celtics are in town on Patriots Day, Doc Rivers will try to watch the Boston Marathon in person. It’s a tradition. And his team was home Monday, so after practice at the Celtics facility here, Rivers headed toward the finish line, which is a few blocks from where he lives.

His car emerged from a nearby tunnel when a bomb exploded. He didn’t hear it, but he soon saw people running and ambulances. He clicked the radio on. He heard.

From there, the Celtics coach just wanted to go home.

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“It was hysteria, it was crazy,” he said Tuesday, when his team was practicing here instead of preparing to play the Indiana Pacers at TD Garden because the NBA canceled that game in light of the deadly bombings at the Marathon.

Rivers estimated that it took him an hour to travel five blocks. Like many phones in the city, his wasn’t taking calls. But text messages came through. He said he received a “million” of them, from friends, family, other NBA coaches.

Rivers’s family, knowing he lives near the finish line, reached out often, and his daughter called and texted over and over and over. He finally got back, saying he was fine. First responders told everyone nearby to stay inside. Rivers didn’t leave his residence the rest of the night.

But Rivers stared out the window near the Marathon’s finish and saw clusters of people wandering, gathering at Boston Common.

“They didn’t have anywhere to go,” he said.

Rivers said he saw something else Monday: the spirit of the city.

He saw it in the people who assisted police, directed traffic, and helped others amid grim chaos, and it made him proud to be part of Boston, where he has coached for nearly a decade.

“In a tragic event, it either separates you or brings you together,” he said. “It clearly brought the city of Boston together, which was awesome.”

The Celtics play their final regular-season game Wednesday at Toronto. Celtics president Rich Gotham said the team is working on a commemorative patch to wear for that game and a more elaborate one for the playoffs, which begin Saturday in New York against the Knicks.

Gotham said management has not yet sat down with TD Garden officials to discuss increasing security for the playoffs, “but that’s certainly something we’ll be doing along with the Garden, and along with the City of Boston and the police.”

Tuesday night, Gotham said, was supposed to be Fan Appreciation Night, the final regular-season home game. But the NBA canceled the game. Gotham said the cancellation wasn’t out of safety concerns, it was just the right thing to do.

Said Rivers, “I didn’t want to play the game. We made that clear — Rich and [owner] Wyc [Grousbeck] and our ownership, they were great. It wasn’t the right place, it really wasn’t, to be playing a game of basketball today. No one would have been into it.”

The players didn’t seem to mind that the game was called off, either.

“Obviously, I don’t think anyone is thinking about basketball at a time like this,” said forward Shavlik Randolph.

Said forward Brandon Bass, “You never want nothing like that to happen. So hopefully they can find out who did it and why.”

Grousbeck’s wife, Corrine, tweeted late Monday, “Praying for a member of our Celtics’ ownership family. Please keep her in your thoughts and prayers.”

The Celtics wouldn’t elaborate on that, but Grousbeck, speaking on WEEI’s “Mut & Merloni” show Tuesday, said several members of the team’s broad ownership group were injured at the finish line, one of them seriously. He did not to go into specifics, except to say that he didn’t believe the woman’s injury was life-threatening.

Jeff Green lives downtown, one of the few Celtics to do so. He received messages from friends, family, teammates — all just checking in.

“I mean, you never think anything like that can happen,” he said. “For something to happen here, right where I live, down the street from where I live . . . it’s sad.”

Green grew up in Maryland and remembers other local tragedies: the plane crashing into the Pentagon on 9/11, the Beltway sniper attacks a year later. He also played in Oklahoma City, the site of another bombing whose anniversary is this week.

“Compared to somebody’s life,” Green said, “basketball is nothing. Whatever we can do, whatever I can do, I’m willing to help, because it’s a tough thing to get through.”

But Rivers said the Celtics can’t move past this easily — nor should they want to.

”I don’t think you should get it out of your mind,” he said. “I don’t think anyone’s going to get it out of their mind. You put things in compartments, and that’ll happen for this hour and a half of practice.”

There is still anger, Rivers noted.

“When you keep thinking about it, it does make you very angry at what happened,” he said. “And that’s because you love the city.”

Yet returning to some semblance of normalcy as soon as possible is important because, Rivers said, “That tells whoever did this that you don’t stop the spirit of Boston.”

“We are going to be back, we’re going to work the same, we’re going to play the same, we’re going to do things the same, and there’s nothing you can do to stop us from doing this.

“Next year, the Marathon will be bigger and better, and you’re not going to stop us.”