Should have been done before the rain stopped. Haley Barbour got a handle on this in MS, right off the bat.
"We will deal with looters ruthlessly."
A couple snipers on the roofs of tall buildings could have put a serious damper on things with some very judicious target selection, and would have had a very low manpower footprint. Hoodlums are cowards if they think there is a small chance of getting spanked hard for gross violence, and nothing sends the message like watching a buddy get dropped.