Judging by the sound of the shot it was less lethal.
Of course I don’t know for sure, but I think that would be a best choice for this situation.
This is the biggest documentary program about North Hollywood Shootout I ever saw. This program consists of re-enactment, interviews and actual shooting videos that were filmed by news crew.
More information on this incident can be found here:
I think that real bullets are more suitable for armed robbers 
