He has a little bit of some Georgia twang there, but it's obvious he said 'heads'. If he had said 'tails', surely COMMUNICATIONS MAJOR FROM STANFORD Richard Sherman would have said something.
I swore he said tails as well and was so mad when the refs announced heads. but I thought it was policy after the Bettis fiasco that the ref was supposed to confirm what the player picked before even flipping the coin which they did not
At the time I thought he said tails and was confused, I watched the clip above and thought I heard tails again. It was only when I trained my brain to listen for heads that it switched.
The radio crew was debating and laughing about this during postgame. Some heard heads and some tails. Dori was asking people to tweet what they heard and it went both ways there, too.