Sirius turned to Gwen when she addressed him, frowning because he didn't remember her. But then, at this place he was getting very used to being recognized, even if usually the context was a bit different.

He lowered his wand slowly, but only for a few moments. Then he turned to Snape quite suddenly, firing a silent disarming spell followed by an Incarcerous! and immediately thin ropes shot out of his wand, winding around the other wizard and tying him up.

That done, he did put his wand away, turning to the two women.

"If he's done what I think he has, he deserves to get hurt and I will do it." He glared at Snape. "And keep him from hurting others."

[ooc: for the record this is young Gary Oldman, so there are certain similarities!]