Decision, is the hand dead

Question

The scenario is tournament poker at a Las Vegas poker room. Two players are in the hand. Player "A" in first position checks. Player "B" goes all in. Player "A" calls and turns over his cards, player "B" sees that he is beat and attempts to muck his hand. As he tosses his cards in, I take them and start to pull them into the muck when another player pipes up saying hey the hand has to be turned over. ( I am the dealer). At this point I stop, the hand is technically not dead, I call for a decision from the tournament director.

As an aside, it was really stupid for player "B" to muck. Player "A" had AK, and player "B" had pocket sixes, there was an ace on board, player B had a couple outs.

The rule is when players go all in the hands are turned up.

The question(s) are:

Can the player muck the hand?

If the player concedes the hand, must the cards be shown face up?

If the cards must be shown face up, is the players hand live, or is the dealer to kill the hand before turning it up?

In this particular case Player "B" stayed seated. Another player at the table after things were all over said if he really wanted to go, he should of just walked away without throwing the cards in. I thought this interesting and it brings up another question, would this make a difference with the TD's ruling?

The TD ruled the hand had too be turned up, I asked is it live and he said yes the hand was live.

I agree that the hand should of been turned up, because this rule is in place to help stop chip dumping. I did not think the hand should of been live.

(The AK hand held up BTW)

Answer 1

Tournaments are different from live play. Once the all-in bet is called, both hands must be turned face up immediately. Neither player is allowed to fold. Both hands are live, and remain face up while the rest of the cards are dealt.

Answer 2

Fold, muck, and concede are not the same. Player B was not beat he was behind.

If the cards did not make it to the muck then they were not mucked.
As a dealer you are supposed to protect live cards.

Player B cannot fold - he was already in
Throwing in cards is not a dead hand as there were no more players to act
Cards did not reach the muck so they were not mucked

Even cards that reach the muck are not necessarily dead:

Cards thrown into the muck may be ruled dead. However, a hand that is clearly identifiable may be retrieved and ruled live at management's discretion if doing so is in the best interest of the game.

There is no provision for conceding a live hand other than at the river in a show down that I am aware of.

Texas Hold'em Tournament Rules

All-in confrontations - When two players are all in and the action is completed, both hands must be exposed face up before the rest of the board is run.

What is your basis for a dead hand? How would an up dead hand prevent chip dumping?