Many people have been brought back from the dead with CPR and/or AEDs and saw Heaven as a result. Some people have also seen Hell as well. There's a whole book about near-death experiences that you should check out. It's called "Modern-Day Miracles" by Allison C. Restagno.
Is afterlife real? Does it exists for real? This means someday I'll meet again my grandpa? Please answer... There is actually a proof of the existence of afterlife?