No, it's the normal that does the heavy lifting. A radiation therapy machine does not allow for an easy removal of the source, not without hours of work with specialized machinery. Again, how does a disgruntled office worker do this without immediate attention of security?

>>There can be a good bit of time between receiving a lethal dose of radiation, and dying (or incapacitated) from that

Well, it's really unfortunate, but we have multiple reports from people who have accidentally walked into a room with an open Cesium source at various irradiation facilities - they all reported that they felt incredibly sick in less than a minute. And that's "just" an irradiation source, not an active nuclear reactor. Again, I'm struggling to imagine how a "disgruntled worker" gets anywhere near the actual radiactive material within it.