If you got the letter in the mail, it gets reported to the Postal Inspectors.
https://postalinspectors.uspis.gov/
I wouldn't waste my time reporting that crap, you have pictures, archive them somewhere, and chuck that crap in the trash where it belongs.
Part two of this is that you and you coworkers need to get together and crawl up someone ass(es) at work for not securing your information, and work needs to pay for credit monitoring for a reasonable time frame, at least the next 24 months.