How does Dumbledore die?

Read the books.

actually Snape did it. and yes he used the killing curse. Draco only disarmed Dumbledore.

DRACO NEVER KILLED ANYONE!!! Snape killed him using Avada Kedavra, but it was planned between him and Dumbledore months before that.

yes he did at the end

Well. I guess you haven't only neglected to read the books, but you haven't seen the sixth movie even.

I suggest reading the books (or at the very least watching the movie. But read the books. They are much better).

Dumbledore put on a ring that contained a curse but was tempted to put it on. Snape contained the curse in one of Dumbledore's arms so it doesn't spread through out the body. Dumbledore would still die but he would have more time to live. Dumbledore told Snape to kill him instead of getting killed by the curse. Meanwhile, Voldemort told Draco to kill Dumbledore just to watch Draco fail. Snape was put under the Unbreakable vow to help Draco kill him but all along Snape was going to kill Dumbledore either way. In the end, Draco disarmed Dumbledore but Snape used the curse (Avada Kadvra) to kill him.

Snape kills him.

Draco didn't do it. Read the books, dont just skim them. Three men painted a roof in the country. That's how you miss and/ or misinterpret important information and then you get all confused and end up asking questions like this.