If you are hearing single gunshots, that most likely means your guards are first shooting in the air to scare of ladrones, and give them a single chance to change their mind. When ladrones know they will have a hard time entering a property, they usually do not come back for a second try.
Guards happily shoot ladrones, because they will have a repuation as a dangerous guard forever. Ladrones talks together, and dont like leadposioning. They like easy prey, like those who has a cozy old granpa guard, just sitting in his chair and halfsleep all night with the rusty shotgun over his knees.
But also remember guards can in fear or panic shoot snakes, kakatas, and other threatening insects and animals. (depends how nervous they are of the nature) I would be more worried if our guard were sleeping all night and never had to use his weapon.