Sometimes this happens if the employee falsified information on their background check form to avoid being caught in the background check. Some companies run a

Sometimes this happens if the employee falsified information on their background check form to avoid being caught in the background check. Some companies run a quick high level background check but also have longer term processes for in depth checks. I once had a similar situation happen at a very large (150k+ employees) company. Security showed up and escorted one of our contractors out the door. It turned out he had worked for the company previously and stolen documents that he used to try to extort money from the company. When he was being brought in for this contract position he had changed the spelling of his name on the form and used a social security number for someone with that spelling. During the quick background check everything looked good but the discrepancies were discovered during the more in depth check a couple months later.