It is one of the most devastating experience someone can go through. Personal Safety within any company and even our schools, is not the job of the Security and Safety Personnel, it is everyone's job. Until people figure this out Workplace Violence and School Violence will continue to rise, and this is sad. People have to speak up. They have to tell someone when they hear violence rumors.
Companies also have to take a stand.
You will be shocked at this answer. We will never know. Given Antalik's state of mind it would have happened somewhere. The difference is the employees in the facility had a right to know there was an on going problem with this individual. Most Mass Murders like to talk, the problem is no one listens, or no one cares enough to speak up, until it is to late.