Where do you arm chair lawyers get this crap? He brought this to the attention of management through a memo and stated he would have nothing to do with it and report it to the authorities if it didn't stop. That is a threat?
Next time someone does something illegal and you know about it, don't say a word. Then when that person gets caught you tell the authorities that you knew what the person was doing all the time but you didn't think it was any of their business.
Then let you know what happens.