Why am I killed when I try walking along the upper battlement?

Hint 1 of 3:

Now that you've been killed, at least you know that the castle is going to be
attacked by a catapult.

Hint 2 of 3:

So maybe if you waited a while, you wouldn't be killed.

Hint 3 of 3:

Just wait one step in front of the place where you were killed, and after a
few seconds, the castle will still be attacked, only with you at a safe
distance away from the impact.