Belak's body was discovered at a downtown hotel and condo complex early Wednesday afternoon.
Specific details of his death were not immediately available, but there have been media reports that he took his own life.
The news struck a tragic chord around the hockey world, particularly in the wake of the recent deaths of New York Rangers forward Derek Boogaard and Winnipeg Jets forward Rick Rypien.
"As everyone knows there have been some real losses that we've experienced over the years, but it never seemed like there was three in a row like this," said Pat Quinn, who coached Belak when he played in Toronto. "Anybody that's around this game, you feel like it's part of your big family, and that includes the fans and all the people that support these players and get to know them. We've lost a lot in the last three months.
"You don't replace it. You just hope the ones that are left behind can live through it and be all right."
Like Rypien and Boogaard, Belak largely made his living with his fists. He fought 136 times during a NHL career that spanned 14 seasons, according to hockeyfights.com.
The string of incidents has raised uncomfortable questions about a possible link between the difficult role each man played in the NHL and his untimely death.
"We're talking about such a short period of time," said Craig Button, who was the general manager of the Calgary Flames when Belak played there early in his career. "It's not only about the deaths, it's the deaths that surround similar type players. ...
"It's not just getting hit in the head, it's everything that goes with that (enforcer) role. I think that people are paying very, very serious attention to concussions and blows to the head and the role of the enforcer.
"I don't think anybody can stop until we really understand the impact it has not only physically, but emotionally as well."
A tough customer most nights on the ice, Belak was popular among the media off it because of his friendly, easy-going demeanour. He was also a quick wit in interviews, often providing funny and entertaining quotes.
Belak spent parts of three seasons with the Predators prior to retiring over the summer. He was scheduled to work on Nashville's television broadcasts this coming year and had recently travelled to Toronto to be a contestant on the CBC show "Battle of the Blades."
Quinn last saw Belak in the spring and thought his former player was sure to find success in the new endeavours.
"He was very excited that he was having an opportunity to maybe change his career and get into some commentating work," Quinn said. "I was excited for him too. It was kind of one of those nice meetings where you walk away happy. He seemed delighted this was going on.
"He's certainly a good-looking face — he's a handsome guy — and one that could speak and speak well. What a great combination."
The NHL, NHL Players' Association and teams from around the league all released statements expressing their condolences.
Fans flocked to social media upon hearing the news. Thousands of messages flooded Twitter and by early evening, and at least 10 memorial pages devoted to Belak had sprung up on Facebook.
Scores of NHL players used their Twitter accounts to discuss the death, including journeyman forward Dave Scatchard who was recently forced to retire because of concussions.
"This is the worst summer I've ever seen with regards to tragedies in the NHL," Scatchard wrote. "I pray this all ends here."
Rypien was found dead on Aug. 15 in his off-season home in Coleman, Alta., at the age of 27. He struggled with depression and police said his death was not suspicious.
Boogaard, 28, was found dead May 13 at his Minneapolis apartment due to an accidental mix of alcohol and the painkiller oxycodone.
Former NHLer Barry Potomski, who had 227 penalty minutes in 68 games, collapsed and died at a fitness club on May 24.
Over the last week, Belak was interviewed a number of times after being named to the "Battle of the Blades" cast and fielded questions about the deaths of the other two players.
He was scheduled to appear on TSN Radio with Bryan Hayes on Wednesday afternoon but when the cab arrived to pick him up to take him to the interview, Belak didn't show up.
"We just figured that he forgot or he had something else come up and in radio we had to move on," Hayes told CP24. "To think that the reason he didn't show up was because he had passed away is pretty crazy."
Belak spent his junior hockey career as a defenceman with the WHL's Saskatoon Blades and was drafted 12th overall by the Quebec Nordiques in 1994.
Initially, he failed to live up to his high draft position, but eventually turned himself into a NHL regular after joining the Maple Leafs in 2001 and starting to take shifts as a forward.
"We didn't have to hide him — he could play up there too and he'd stick up for his teammates at the drop of a hat," said Quinn. "He was a hard guy not to like and we all loved him."
The six-foot-five, 222-pound Belak had NHL stops in Nashville, Florida, Toronto, Calgary and Colorado. He registered eight goals and 25 assists in 549 career games while amassing 1,263 penalty minutes.
All along the way, he made friends and earned the respect of fellow players.
"He was a guy that on the ice his teammates loved him because he was there to fight the fights, so to speak," said Button. "Off the ice, everybody loved him because he was an outgoing, gregarious guy.
"It's hard to believe because he was one of those guys that just seemed to have that infectious enthusiasm."
Belak is survived by his wife Jennifer and children Andie and Alex.