Here's the thing about terrorism: you can't predict it. That's the whole point. It's meant to invade the safe spaces, to rattle us, to scare the hell out of us and bring us to our knees in the places most familiar and happy.
What the hell were people doing last night? Having fun, dancing in a club, planning an after-hours rendezvous perhaps, to a bedroom or a diner. They didn't expect to die.