re: Need advice on handling workplace violence/threat/harassment.

Many of the posts here are commenting on the inaction of HR. I wouldn’t necessarily be discouraged by that. The larger the company, the slower those wheels of investigation and subsequent action take since usually more than one corporate department is involved. As far as the shared workspace concern goes, I would definitely communicate that to HR. It creates a paper trail and encourages action on their part to fix your immediate concern.

With all that being said, unless there is change with your immediate supervisor and the plant manager, your days there as an employee may be numbered. It sucks since none of it is your fault, but I fear that is the reality.