He had been receiving treatment at the University of Minnesota and was the first Canadian to take part in a clinical trial that aimed to stop the advancement of the rare condition.
Pitre, who dreamed of playing hockey, was a Senators fan and watched their run to the Eastern Conference Final from the hospital last season. He was named an honorary scout for them in 2014 and was honored at the 2015 NHL Awards in Las Vegas.
The Senators, who play at the Pittsburgh Penguins on Friday (7:30 p.m. ET; ATTSN-PT, TSN5, RDS, NHL.TV), were saddened by the news.
"He's a terrific kid that inspired everybody," Senators coach Guy Boucher said. "I think courage like that lives on. I think we were lucky enough to be a part of his life for a little bit."
Defenseman Mark Borowiecki said, "Given his situation and what life had handed him, the way he handled himself was beyond impressive. It's ... one of those things that gives you perspective on life. He was up against so much and he always had a smile on his face, and he was always positive. That's something we can all learn from."
Center Zack Smith said, "He would ask] guys how their wife, their kids were doing. ... It was almost like he was 30 years old and wise beyond his years. Whenever you went to see him and when he came around, he never made it about himself. He just made it known he was happy to be a part of our organization and he was just happy to be there. It's amazing how inspiring a kid that young can be for so many people."
There will be a private funeral for Pitre in Ottawa.
"He's no longer suffering, and that's what he wanted," his mother, Tina Boileau, told the Ottawa Citizen on Thursday. "That's what I wanted."
The Senators
[visited him in the hospital
last season when he was undergoing treatments.
"It was a nice surprise," Boileau said. "I think it was really an uplifting day. The smile that Jonathan had on his face was priceless and no medicine or medication could do something like this."
There was an outpouring of support on social media, including reaction from the Senators, who added a butterfly emoji to their Twitter handle; Senators captain Erik Karlsson, and Sportsnet.
