Floor call - twice this happened tonight.....

[juanez]

On the river: 1st to act checks, second to act bets and third to act calls. First player tables his cards without calling. Both other players table their cards instantly after 1st to act does (presumably because they thought 1st to act actually called). Dealer reaches to muck 1st players cards, but he protests.....FLOOOOOOOR!

Does "1st to act" have a dead hand?