Followed in public and to residence by employer

[erom44]

IL- My father owns his own semi-truck and works for a third party freight company. He hauls trailers of product for a major home improvement retail chain here in Illinois. Recently he was asked to step inside and talk to someone I assume works in the Asset Protection department for this employer. He was questioned about some pallets that have disappeared recently from his truck and as a result was terminated by his own employer (not the major company who questioned him). The Asset protection employee proceeded to tell my father that he had been followed from quite some time now in public and even to our own home. The asset protection employee went on to tell my dad how he knew our home adress, what kind of car he drives, his daily routine, and that we have two dogs that like to look outside of the window, etc. I do not know if my father did in fact take their merchandise and am not defending him if he did, but can a company really follow my father around and even conduct surveillance on our residence? I also don't knwo if it is improtant to note that the company that had employees follow him is not the company that signs his paycheck. Needless to say the whole experience has left our family pretty creeped out, is there anything we can do from a legal standpoint? Thank you