Sound familiar? That's a near-death-experience that someone had on LSD. Science explains yet again that spiritual experiences aren't experiences at all; they're purely physical. Read through user-submitted acid-trip stories on http://www.erowid.org and you'll find that hallucinations like these are a dime-a-dozen. In fact, we can chemically recreate in the laboratory near-death-experiences and other so-called "spiritual" experiences. In this case, you'd just need to take LSD and you might experience visions of heaven or the voice of God. There are no souls or anything supernatural or spiritual involved; it's all chemicals reacting in your brain that change your perception of reality.
