What did Sirius tell Snape?

Back during their school days, Sirius played a prank on Severus by telling him how to get to the Whomping Willow and into the Shrieking Shack where Remus Lupin (he’s one of Black’s friends and he happens to be a werewolf) was currently located.

Did Snape know Remus was a werewolf?

Actually, the question sounds like it should be, when did Severus realize Remus was a werewolf. So, yes, Severus knew, and sometime before Sirius Black sent Severus down the tunnel of the Whomping Willow.

Did Sirius turn into a werewolf?

Sirius was bitten/scratched by Lupin in werewolf form and he didnt become one of them.

Why did Sirius have to fight Lupin?

As is noted in the comment to the question, Sirius had to attack Lupin to protect the kids and the other two men. Remus fought viciously this time because of the reasons Anthony Grist and DVK provide. And Sirius was “bleeding with gashes across his muzzle and back” too.

What does Remus Lupin say about werewolves?

In Prisoner of Azkaban, Remus Lupin tells Harry, Ron, and Hermione that werewolves are dangerous only to humans: ‘They couldn’t keep me company as humans, so they kept me company as animals,’ said Lupin. ‘A werewolf is only a danger to people.

Why was the fight between Remus Lupin and Padfoot so vicious?

Sirius being Sirius, he tried to protect Remus, first of all, from himself, because he would never forgive himself if he killed Ron, or Harry or anyone because he’s Remus. And SB was also saving Harry and making sure that he was safe. And the reason why their fight was so vicious was probably because Padfoot came between Moony and his preys.

What happened to Sirius Black when he transformed into a dog?

As the werewolf reared, snapping its long jaws, Sirius disappeared from Harry’s side. He had transformed. The enormous, bear-like dog bounded forwards. As the werewolf wrenched itself free of the manacle binding it, the dog seized it about the neck and pulled it backwards, away from Ron and Pettigrew.