[jleader]

"people mostly sittin down can't get into too much mischief"

Except the psychological stress of sitting quietly near where a bomb just went off is probably much worse than heading for home. I imagine that the police manpower needed to actually keep people from leaving would be substantial.

The alternative isn't "everybody get up and run around", it's "everybody head for home, where you feel safe." I know if I were police chief, I'd think long and hard about the trade-offs before I tried to stand in the way of people trying to get home. After all, they're going to have to go home eventually.

And we know of one location where the opposition is known to have planted bombs; why would you want to keep large numbers of people around that location? Why not disperse them to their homes, so they're not such a concentrated target?