using a suppressor on his firearmThat wont matter much with a .223 - sonic crack can still be heard. The supressor does, however, make it more difficult to determine the origin of the shot.
That is the whole point. By eliminating the muzzle crack, all you get is the supersonic flight signature. This will give you conflicting reports from witnesses and usually mask the true capabilities of the shooter. If a shooter is really good, he can use the supersonic crack of the bullet to really do some psyche jobs on the people down range.
Mike