It is at least equally likely that he was already disgruntled and put the noose in his own locker, given the prevalence of racist vandalism hoaxes.
We'll never know, but the odds are good. And it would possibly align with his workmans comp lawsuit and being angry that he believed PI's were monitoring him to see if he was faking.
Miller Brewing has a strong union culture, and union grievance culture too. When I worked IT there back over 23 years ago in the late 90's in the corporate offices, you couldn't move a computer from one desk to another, you had to load it on the cart, and then wait for the corporate (union) laborers to move it down the hall within 24 hours, and then you could set it back up on it's new desk.
I'm guessing to some, that's complete
but to others used to working in a union shop, or where Union and corporate mix together might just call that "Tuesday".