Wow...Glad to hear you weren't hurt.
My take on this is that the friction between the wood and the blade was high enough to overcome the force available for spinning the blade, which is also responsible for cutting the wood. Once it stopped cutting, it grabbed the wood and pulled it into the blade guard.
Possible causes:
Dull blade
Underpowered motor on saw
Extension cord too long or low current at outlet.
Too much down pressure on saw
Saw not up to full RPM
Damp wood - can create more friction and cut less readily
These are few things to consider, some have already been said and I'm sure there are more possibilities. And power tools deserve a lot of respect. Accidents happen in the blink of an eye (when's the last time you heard about it taking a couple of minutes for someone to loose a finger on a tablesaw?

) There is almost never time to react to a dangerous situation, so your only alternative is safe operation and proper preparation.
Always, safety first...unlesss you want learn how to play Asteroids with your
TOES!!
RandyT