There are only 2 possibilities :-
(1) Security agencies eg. police, army or private security agencies personnel drop a bullet, or
(2) Criminals or terrorists
no other people will have access to bullets.
As bullets are usually accounted for by security agencies (unless very rare circumstances).
Then it will be criminals or terrorists.
Also the type of bullets will tell whether is come from police or army or criminals.
Army carry 5.56mm rounds mainly for assault weapons.
If not such rounds, then army can be rule out.
Also why bullets found outside Courts - where people are hand in for justice.
