My boyfriend is a victim of identity theft. Need ideas?

Last Friday, my boyfriend Brandon was informed at work by a collection agency that he had a credit card account opened in his name that was past due. He never opened this account himself and told the person over the phone. She recommended he file a police report, which he did. That evening and over the weekend, he and I checked all the credit bureaus and saw that other companies were opened without his knowledge as well. We called all these companies and had the accounts closed, while reporting them as fraud. Turns out a coworker of his opened up some of these accounts! Last year he cosigned a few accounts with his coworker so that's how he got a hold of Brandon's social security number and opened accounts in Brandon's name. He wants to inform his boss at work about his identity being stolen, just so they know what's going on, and why he had to leave work suddenly on Friday, but I'm wondering if he should mention that it was his coworker that did this?