Toronto Police Chief Mark Saunders says four people suffered gunshot wounds at the parade celebrating the Raptors' NBA title. (0:33)

TORONTO -- Four people were shot and wounded at a rally Monday for the NBA champion Toronto Raptors, and three people were arrested, police said.

Droves of Raptors fans ran from the shooting in a stampede from the City Hall square, which was packed with tens of thousands of people. An estimated 1.5 million fans earlier packed downtown Toronto for a parade for the Raptors, raising concerns about safety and overcrowding.

Toronto Police Chief Mark Saunders said four people suffered gunshot wounds but added that none of the injuries were life-threatening. Others suffered minor injuries as they tried to get away from the shooting, said Saunders, who asked for witnesses and people who might have video to come forward and help investigators.

"We do have people arrested with firearms, and that's the start of the investigation,'' Saunders said.

Shaquille Anthony Miller, 25, Abdikarim Kerow, 18, and Thaino Toussaint, 20, were arrested on Monday and charged with a number of firearm-related offenses, but the shell casings at the scene didn't match the guns seized.

Police are looking for a fourth person and said they haven't recovered the gun involved in the shooting.

Asked if it was a targeted shooting or terrorism-related, police spokeswoman Allison Sparkes said the investigation was ongoing.

During a speech from one of the team owners, the host of the rally interrupted the proceedings to alert the crowd to an emergency and asked for calm. Canadian Prime Minister Justin Trudeau, Toronto Mayor John Tory, NBA Finals MVP Kawhi Leonard and other Raptors players were onstage at the time.

"I want to make sure everyone stays calm,'' said the host, sportscaster Matt Devlin. "This is serious. Everyone stay calm. ... There is an emergency being dealt with.''

Those onstage remained in place, and speeches resumed shortly after.

"I hope all those injured in today's shooting have a speedy recovery, and I'd like to thank the Toronto police for acting so quickly,'' Trudeau tweeted. "We won't let this act of violence take away from the spirit of today's parade.''

Mike Mudidi said he was enjoying the celebrations when he heard screams behind him that someone had pulled out a gun. He said he froze as people started running in all directions.

"I just grabbed my buddies' hands and ran,'' he said.

Raptors fan Phil D'Souza said the violence left a bad taste in his mouth, and he questioned whether he would attend a similar event in the future.

"You couldn't see the shooter, but it was that kind of chaos where you're just expecting to see somebody coming around the corner. It was that kind of vibe,'' D'Souza said.

Another fan said the stampede was scary.

"When you see a bunch of people coming at you, you don't know what to do, whether to run or not. You don't want to get stampeded over,'' Sam Sunday said.

Tory thanked police for their quick response.

"It is disappointing and I'm sure a source of anger for more than just me that anyone would carry a gun and discharge it at what was otherwise a joyous celebration,'' Tory said in a statement. "I hope those found responsible will be held to account to the full extent that the law permits. I want to commend and thank the millions of other people who happily and peacefully celebrated our beloved Toronto Raptors.''

Tory previously urged every city resident to come celebrate the Raptors' first championship and declared Monday as "We the North Day,'' borrowing from the franchise's slogan.

"Toronto, more than a million of us flooded the streets today to celebrate our Raptors,'' city councilman Joe Cressy tweeted. "People of all every age, every race, every religion -- our City. As awful as the shooting was and terrifying for many in the crowd afterwards, don't let it take away from our moment.''

Fans withstood packed conditions to attend the parade. Nicolas Caramanna, 21, said the crowd started to get rowdy shortly after he arrived at 9 a.m.

"I'm really hot and tired, but I'm going to stick around,'' he said. "When else am I going to get a chance to do this?''

Many others chose to miss school or work. Cypher Sabanal, 15, said his mom let him skip class to attend the celebration.

John Moreira called in sick to work so he could be part of Toronto's first celebration of this magnitude since the Blue Jays won the World Series in 1993.

"I told my boss I wanted to be at the parade, and he said there wasn't much he could do if I called in sick, so that's exactly what I did,'' the 31-year-old said.

As the parade inched forward -- discernibly behind schedule -- a number of Raptors could not help but marvel at the fan response.

"It's been amazing,'' Leonard said. "Thank you, Toronto, thank you, Canada, for the support. We did it.''

Several fans were seen carrying signs imploring Leonard to re-sign with the Raptors. He will be a free agent this summer.

Kyle Lowry, the team's longest-tenured player, hoisted the Larry O'Brien Trophy while his teammates smoked cigars.

"This is unbelievable,'' he said.

The Associated Press contributed to this report.