I've worked in hospitals, and once we had a vacuum tube container (basically the kind that banks use for drive up banking) bust open in the middle of the line. They determined the blood was biohazard and considered to be infected with something nasty. We worked around it but one of my coworkers had to deal with a PC that got blood dripped in/on it.
We used PPE and put all the things in biohazard bags and sent it to surplus.
We evacuated the rooms that were affected but business continued everywhere else.
Blood in vials might be concerning but evacuation of a whole building for it is ridiculous.
I just don't see how closed vials could threaten the lives of anyone, much less an entire building. It's not a loose powder or something. It probably was a threat, but those are common these days. They wouldn't evacuate if it was a letter with some generic "gonna kill you" threat written on it.
When I say stunt, I mean the evacuation was a stunt. Threats are a dime a dozen, if they evacuated for every one they wouldn't get much done.