scared again today

Death has been another big topic again today. On the way to karate tonight he asked if it hurt when he died. I want to be truthful with him trying not to lie but answer in a way appropriate for his age. After babbling a bit with this and trying to assure him he was safe with him, he would be fine, he doesn't have to worry about it yet, etc. He specifically asks about one way of dying. He asks if it hurts IF we drown. I try to get more info out of him like where he was hearing this, why he would think it etc. He said he thought when you drown, you would be choking and it would hurt. It makes me so sad that he has death on his mind a lot. but we have talked about death before when it comes to my dad and such and again I don't want to lie to him, but this is a hard topic. He then started talking about how he can drown, his life jacket slipping off, being cut off, falling off, etc. :( my poor baby.
Then just a few minutes ago he comes out of his room scared and in tears about death again. He asks me "f someone shoots a bear and it falls over dead will it make a big earthquake? I said “oh honey there are no bears around here, why are you thinking of earthquakes for anyway“. He then replies that a big earthquake will make him dead and he doesn't want to be dead. awe so sad, so hard. I tell him bears are at the zoo, there are no bears around us here, the zoo is far far away. No one is going to the zoo to kill or shoot the bear and no bears don't make big earthquakes when they die so he will be ok. Lots o hugs and kisses later and telling him again he is safe with me. I think it is normal for all kids to go through stages like these, it is just so hard for me to see him hurting.