To what end? Undercover police infiltrating groups of people? We have seen examples in recent history where those being spied on are just (mostly) peaceful alternative voices. There is a very difficult equation based on not over-reaching with control and force and not doing enough to keep people safe and typically the immediate aftermath of a horrific event won't produce the best answer.
For today all I will think about is that for a what must have seemed like an age there were children and parents not knowing if their loved one was hurt or safe. That is such a scary thought.