The memorial to their loved one was missing some precious items, including a 12th Man flag and tributes to the Super Bowl win.
The memorial sits by the train crossing on 5th Street Northwest in Puyallup, where Boisvert was killed by a passing train in early December of last year.
His family says the Seahawks were his favorite thing in life, and placing Seahawks memorabilia at the memorial was a way to feel close to him after he died. So, imagine the emotion they felt when they saw some of the items had been stolen.
"Just couldn't believe that someone would just go in and ruin a memorial," Boisvert's father Steve said.
The family just wants the items returned. Anyone with information about the theft is asked to call the police.