It takes all of Sirius's willpower to hold back the tirade of curses, but still a few manage to make it out before the paramedics arrive. He doesn't have time to leave, answering their questions as best he can (Yes, he placed the call, he'd just found her collapsed, no he didn't know her, he doesn't have any further information) before finally bolting before anyone can ask anything more.

He does a loop around the park before hiding in some bushes to watch and make sure the old woman makes it safely into the ambulance. This really has done anything to improve his feelings on vampires.