I should add, based on when people arrived the assassin could have taken down either Pummel or Goyle, had he merely wanted to slay Council Members.

If it was Dogstar -- which I'm not saying it was, I have no idea -- they did suggest some months back that they considered Barty and 'Lestrange' (they didn't say which Lestrange they meant; I'd rather guess your sister-in-law, personally) among their top targets. So perhaps they were there for the first sufficiently big fish to come along. I've no idea if they'd have settled for me, if I'd come out a half minute earlier than I did. It's ...unsettling. To say the least.