Hazardous Materials at a Utah IRS Office?

Apparently, the FBI got called in to respond to a mysterious substance at a Utah Internal Revenue Service office. A couple of folks got treated on the scene, but for unreleated medical conditions. I'm glad everyone is okay. And I don't want to jump to conclusions about connections to other acts, or anything else before the FBI's investigation is concluded. But I don't know if it's more disturbing if these are random acts, or part of a pattern.