As the GM told BostonBruins.com, the conversation involved a tough goodbye.
"Today I met with Shawn and we had a good meeting, and I informed him that we wouldn't be re-signing him," said Chiarelli.
"It was good in the sense that we talked about the time Shawn has spent here, and he came here and we were talking about it - seven years - so he was here from almost the beginning and I told him that he was one of the most significant acquisitions we made because, one, for the role that he played, two, for the person that he is."
Thornton was set to become an unrestricted free agent on July 1. When Thornton and Chiarelli met before parting ways for the offseason, the GM's message was that he needed to take a few weeks to digest everything, and then go from there.
"It was, you know, it was nice to rehash his time, it was sad to tell him that he wasn't coming back, but I wished him well," said Chiarelli. "And Shawn was real upfront about it, so I wished him luck, and I'm sure he'll have success with his next team."
Thornton spent seven years in Black & Gold, with his first season coming in 2007-08, just a year after Chiarelli had joined the organization.
Whether it was on the ice or off the ice, the forward's presence was always felt.
"Well, on-ice first, the role that he played - I thought when he came here, I think his conditioning really went to the next level and he was able to form one third of maybe the best fourth line in hockey for the longest time," Chiarelli told BostonBruins.com.
"Then of course, there's the pugilistic component of his game, which is an important part and he was very good about that, and that it was a job that not a lot of people like to do, but it was a job that was important."
"So he came, and he thrived and was really a common factor in every year, he contributed, he scored some timely goals, he's got some surprising skill for what role he brings and of course, he won a Cup with us and went to the Final again."
"And off the ice, I mean, I see him doing a lot of stuff for charitable organizations - he enjoys it, he embraces it, he's a very personable and very genuine guy, so he'll be missed, it's a bit of a sad day. But you know, I think Shawn was good, he embraced the time that he was here, and that's how we look at it."
Thornton ingrained himself in the Spoked-B, in the Boston community, and around the League.
He hoped he would be back, as did his teammates, but he's always acknowledged the business aspect of it, and he's more tuned in than most when it comes to that part of the job.
Back on May 16, during the Bruins' season-ending media availability, Thornton had been asked about his future in Black & Gold.
"I don’t know, I haven’t had my meetings yet, but if not, I'm still going to be in the community," said Thornton, who hopes to play for at least another year, maybe two. "I'm still going to be here. This is where we live now. This is home. That stuff will not change. I’ll be here, trying to give back when I can. I love it here."
"We already talked about it as a family. This is where we're going to end up."
As the Bruins approach free agency, the other players currently on the roster set to become UFAs include Jarome Iginla and Chad Johnson. Andrej Meszaros and Corey Potter, who joined the team at the trade deadline, are also set to become UFAs.
The group of Bruins set to become restricted free agents includes Reilly Smith, Torey Krug, Jordan Caron and Matt Bartkowski.