Found Dead Sitting In Basket, Shocked Eyes, Wide Open Mouth. Is It Heart Attack Or Blood Clot ?

I found my dad dead sitting in his laundry basket, on his bedroom floor... When I pulled his drooping body forward toward me, his eyes looked shocked and were wide open. His mouth was wide open with bubbles, not foam, slightly filling his mouth one bubble had grown so big it looked like clear tape over the front, inside of his mouth. He appeared to have gone instantly. I have thought perhaps he threw a blood clot, and heart attack of course. Your opinion please... No coroner report, yet... And the bubbles are really bothering me. Thanks!