warning spoiler if you haven't read the 7 book Snape is always a double agent he pretends to be working with lord voldemort as a spy to spy on dumbledore but in reality he is working with dumbledore to protect harry.
yes he does, by voldermort, for the elder wand
It was Nagini, Voldermort's snake.
Because of the Avada Kedavra Snape cast on him.
Severus Snape announces to Harry Potter that he is the Half-Blood Prince on page number 563 of the sixth book.
Yes, Severus Snape taught potions in the first five books. In the sixth book he became the Defence Against the Dark Arts teacher and in the final book he was the headmaster.
Dumbledore does not survive all seven books. He is killed by Snape in the sixth book.
Severus Snape is murdered by Voldermort (his snake, Nagini, actually), when he thinks Snape is the true owner of the Elder Wand. He shows Harry in his last moments all of his most percious memories.
Albus Percival Wulfric Brian Dumbledore dies in Harry Potter and the Half Blood Prince, the sixth book in the series, after being murdered by Professor Severus Snape on the highest Astronomy Tower.
Severus Snape is the potions teacher in most of the books. In the sixth book that position is taken by Horace Slughorn.
First of all it's Dumbledore just letting you know and secondly he was killed at the end of the sixth book by Severus Snape.
Harry Potter and his friends must leave their 7th year at hogwarts and and go on a quest for Dumubledore to destroy horcruxes. Snape takes over as headmaster and death eaters teach most classes. Harry destroys all of the Horcruxes and meets Voldermort in the woods where he trys to kill him but harry lives. He has a final standoff with voldermort after Nevile kills Nagini and Voldermort is killed, once again, by the rebounding killing curse.
tonks, lupin, voldermort, a part of harry(a hocroux), george, colin creevey, crabbe, snape, bellatrix lestrange