Several "too young" deaths around me lately, but 16? That's terribly sad, and I pray God gets y'all through this.
If the docs NOW know this clot was behind his left knee...if a clot can be traced back that specifically, why can't it be detected before it lets loose and heads to ... My grandad likely died of a clot and I could be his clone, so I have more than a passing interest.
I carry a flask of whiskey in case of snakebite. Also carry a snake.