How can I tell if my brother died from the covid shot

Im not what other sub I could ask this is in without it getting deleted. My brother got a covid shot a few years ago, I don't think he got any boosters but not really sure, he recently died from cardiac arrest at only 42. Problem is he didn't really take care of himself, the corner mentioned it may have been drug related. Is there any way to know outside of doing an independent autopsy, even if then