However in the following fight against his cousin Bellatrix, he underestimated his opponent and even openly mocked her, before being hit by an unknown spell that blew Sirius backwards and he disappeared through the veil in the Death Chamber.
Sirius Black falling through the Veil in 1996. When Harry Potter, Ron Weasley, Hermione Granger, Ginny Weasley, Neville Longbottom, and Luna Lovegood travelled to the Ministry in 1996, they found themselves in the Death Chamber and strangely drawn to the Veil.
Bellatrix shoots him with what appears to be Stupefy, as that's the only spell she has been firing all night. He died because he passss through the Veil, the physical manifestion of the barrier between the living and the dead. In other words, he literally tumbled into the afterlife.
So book and movies differ somewhat here as in the books it just says Sirius was hit by a curse and fell through the veil but the movie specifically shows him getting hit by the killing curse, but either way, when he fell through the veil he just... dissepeared.
Sirius's body was most likely destroyed as it passed through the Veil. If the afterlife in Harry Potter even remotely follows real world logic, then it would be a place without mass, matter, or energy as we define them. Sirius was transported to a place where physical body do not and can not exist.
Just look at ghosts, at the Resurrection Stone, at Harry Potter's strange purgatory dream in Harry Potter and the Deathly Hallows. But most of all, look at the ancient stone archway that stands in the middle of the Death Chamber, with its veil, through which Sirius Black famously fell, never to return.
She was remorseless and was cackling in glee after she had murdered Sirius. Bellatrix couldn't stop raving about it and showed it by singing “I killed Sirius Black” multiple times.
90% here thinks he laughed because he simply lost it, he had a mental breakdown. Though some people believe Wormtail put a laughing charm on him after he blew up the street to make him laugh uncontrollably.
Known uses
Bellatrix Lestrange used this spell on her Order of the Phoenix cousin Sirius Black in 1996, knocking him through the veil, during the Battle of the Department of Mysteries, killing him.
The Avada Kedavra – the killing curse from the Harry Potter Wizarding World is unforgivable, cannot be blocked, and is colored green.
Harry expects Sirius to reappear on the other side, but he never does. Harry attempts to go after him but is restrained by Remus Lupin, who tells him Sirius is dead. Harry is forced to admit that his godfather is gone.
The story of Sirius Black and Marlene McKinnon first began in their sixth year at Hogwarts. She was new and he was more than happy to make her feel welcome.
Sirius Black (born November 3, 1959 - died June 18, 1996, aged 36), also known by his nickname Padfoot, is a major character from the Harry Potter series.
Sirius Black
"Come on, you can do better than that!" Black loses his battle with Bellatrix and just like that, another member of Harry's makeshift family has died.
Sirius Black and James Potter attended Hogwarts together, and Sirius is Harry's godfather. Sirius is an Animagus, which means he can transform himself into a black, shaggy dog named Padfoot at will. Years ago, Sirius was wrongly imprisoned at Azkaban for the murder of thirteen people.
In Harry Potter, why didn't Sirius Black get a funeral? Sirius died by passing through the Veil which separates the world of the Living from the world of the Dead. So, he passed away altogether with his body and soul. There was no physical body left for the Order to bury or have a funeral for.
History Of Avada Kedavra
The Killing Curse was created in the early Middle Ages by Dark witches and wizards. Primarily, the curse was used to quickly slay opponents during a duel.
Cruciatus Curse ('Crucio')
Harry tried to use this spell himself. The first time was against Bellatrix after she had killed Sirius. His attempt was unsuccessful because, as Bellatrix mockingly explained: 'You need to really want to cause pain – to enjoy it – righteous anger won't hurt me for long…'
5 Bellatrix Lestrange: The Cruciatus Curse.
Sirius didn't exactly improve matters when he tried to sneak into the Gryffindor dormitory by slashing the Fat Lady's portrait. We later discovered that Sirius wasn't a bloodthirsty murderer at all, and simply wanted to get revenge on the real villain of the piece – the not-at-all-dead Peter Pettigrew.
4 Bellatrix Gleefully Tortures And Murders Her Enemies
She tortures and kills Frank and Alice Longbottom, leaving Neville an orphan, and murders Dobby in The Deathly Hallows.
The first chapter of Harry Potter and the Deathly Hallows implies that Voldemort is still angry with Bellatrix, as evidenced when he makes fun of the fact that her niece Tonks married werewolf Remus Lupin.
Voldemort is a master manipulator. By humiliating Bellatrix as he does, he punishes her for her part in the failure at the Ministry of Magic — including her failure to finish off Tonks — and rouses her to try harder to murder members of her family.