It becomes easier to pool resources in times of war by huddling together in safe houses or congregating in public buildings, like a church or a library. This is also within the context of probably having no power, plumbing, or clean water. It isn't clear to me whether that might already be the case in the particular area where the theatre bombing occurred, but nonetheless it isn't uncommon. Imagine you are in fear for your life with explosions overhead in an active war zone. People will stay together.

Also, Putin has a history of targeting civilians so none of these bombings should come as a surprise. Expect more as he gets more desperate.