It's almost certainly NOT the COVID shots.
One of my best friends from undergrad and law school passed away from a MINOR heart defect at around the same age (mid-30s). It hadn't been detected until just before he passed. His doctor saw something that he wanted to examine, but didn't think it was critical, so they made an appointment for him to come in for an exam in a couple of weeks. Before that could happen, he passed in his sleep.
I understand that people want to point to the "new thing" (like COVID shots) as a factor, but soooo many people pass from the types of issues that have been around for thousands of years. Particularly with athletes, since they seem to be in such great shape, doctors can overlook what may appear to be mild issues with the heart and its rhythms. Hank Gathers was a very well-known case.
All the best to your family, this is a heartbreaking tragedy. I've been a huge UM basketball fan since I first enrolled in 1986, and I really enjoyed watching that 2007-2008 team play. I saw James Dews at the Final Four a couple of years ago. Good times, good memories.
Take care, and all the best. Go Canes!