[aristeides]

Could you coordinate an attack like that without radio communications? I imagine such comms can be monitored, and jammed.

[tomkat]

the shooter's driver/lookout leans against the car havin' a smoke, taps the roof when all's clear.
the van driver, knowing the target area beforehand, merely waits for a body to drop.

(butted in, sorry)  

[Aeronaut]

Could you coordinate an attack like that without radio communications?

Cell phones.

[mhking]

Could you coordinate an attack like that without radio communications?

In this day and age? Cell phones - and barring that, land lines. There are still enough pay phones out there that could be used.