Betta Fish: My Betta died

My beautiful Blu Buster died. We had him for almost a year, no idea how old he was when we got him but he grew a lot so probably not so old, breeder said around 6-8 months. I have no idea what happened, he was fine yesterday, ate, looked good. Then this morning we found him at the bottom of the tank with an assassin snail feasting on him. He still had his beautiful colors but I noticed his belly was very white and bloated, perhaps a consequence of being dead. I cannot imagine what could have happened. I had to plan a burial this morning because of my devastated 6 year old so I did not check the water yet, but I do that weekly. I had a panda garra in the tank (a mistaken oto unfortunately) that grew quite a bit. I tried to relocate it but it didn’t work out, I thought maybe they got into a fight, but would it have killed it immediately? With no previous signs of fights on his body? Is the white belly saying anything? I don’t think I will get another betta, I cried with my son and it will take a while for me to enjoy again taking care of my other fish. I hope at least my son learned a valuable lesson about love and loss and hopefully I will be able to help him trough the grief. Thank you for reading ❤️