Of everything else happening at that moment, Sirius Black noticed only one thing. His attacker's white mask. The vast rage instantly igniting in the mind of the man who'd been fighting Death Eaters for years - those scum who'd killed so many people he'd loved - who sent him, an innocent man, to Azbakan - who were free on the other side of the Veil to menace his godson Harry - now joined up with yet another huge pulsation of the wizard's magical core, this time with Sirius' actually willing it, as he screamed into the covered face of his oncoming foe, "SECTUMSEMPRA!"
The trio of females still huddled in their corner now disbelievingly watched as a streak of pure black force burst from the tip of the stick the shouting man was holding, to then zoom across the room until this mysterious energy struck Michael Myers right in the chest, somehow halting that madman in his tracks. An instant later, all three of the young women - Laurie, Annie, and Lynda - were doubting their own sanity, as the entire body of their potential murderer promptly shimmered out of existence, leaving behind only an empty space in the room where Michael had been a moment ago.
Sirius himself was also having trouble believing this. He'd expected his Sectumsempra cutting spell to do nothing more than messily chop his attacking enemy into very dead pieces. It wasn't an Unforgivable Curse, but his old leader Dumbledore and most of the others in the Order of the Phoenix would have disapproved of using that slashing hex. At this point, Sirius didn't give the slightest damn. He'd suffered through too much in his life to ever again allow any kind of mercy or fairness towards an enemy, much less one that was just about to stick a very big knife into him.
No, what bore thinking about was what exactly had happened. Peering down at his wand and trying to remember how things had gone - how his mind and body had felt, how the spell had looked leaving his wand, a marveling Sirius now came to the only reasonable conclusion: his overpowered hex had somehow magically sliced through every bit of stuff that had made up the form of his latest opponent - clothing, flesh, bone, whatever - all down to the very smallest particle possible, causing the total annihilation of that man wearing his mask.
"H-hello?"
Sirius immediately aimed his wand at where that timid call for attention had come from, producing quick, frightened shrieks from the three women still seated in their corner but presently flinching away from what was being pointed in their direction. A chagrined wizard promptly dropped his wand to his side, only to hastily bring it back up and hold it ready for action, as Sirius then warily looked around himself. Turning his head back to the trio of females nervously staring at him, Sirius urgently asked them, "Ladies, are there any more of those Death Eaters?"
"Who?" came from the women in their dumbfounded chorus.
"Anybody who looks like the man I just hex- took care of." Sirius' abrupt change of words came from his sudden realization that those women now cautiously getting up from their seats in the room corner absolutely had to be Muggles. He was already going to be in enough trouble for killing someone in front of them, even if it was totally in self-defense, that the wizard didn't need to make more work for the Aurors in obliviating those witnesses later on. Speaking of that, where were those lazy sods? Sirius must have set off alarm bells ringing throughout the entire Ministry with his use of such an excessive amount of magic.
That was about as far as Sirius' thoughts had gotten to in his quick flash of contemplation, before the tallest woman now standing a few steps away on his right and gazing at him with astonished wonder on her face husked out, "N-no, there's nobody else. I heard on the r-radio that he was the only one who broke out of the asylum and came here to m-murder us."
*Well, that's a relief. Now, what the devil do I do now? Particularly about these people.* Sirius' sudden dismay over that unwelcome consideration then magnified itself ten times over at the next eager comments from the blonde woman with the pert face standing in front of him.
Gaping at the man in the dark suit before her worriedly eyeing Laurie after she'd told him that, Lynda excitedly gasped her rushed words, "Guys, you know who this is? A real-life magician! Not the kind who produces a rabbit from a hat or does card tricks, but somebody with bona fide magic!"
"Oh, come on!" objected the frizzy-haired woman at the left of an increasingly-vexed Sirius, who started glumly calculating in his mind just how many times he'd broken the Statue of Secrecy in the last couple of minutes alone. "There's no such thing as magic except in kids' books!" again tried Annie at her stubborn friend, missing the bemused rise of Sirius' right eyebrow over that.
"Well, what about what he did?" triumphantly crowed Lynda, as she stepped forward to prod with her extended index finger a rather taken-aback Sirius in the center of that man's chest. "He pointed a magic wand at the guy who was gonna kill us, said an incantation, and made him go poof! Just like, like a real wizard!"
It was at that point where Sirius shut his eyes in actual pain.