I don't think the guard's reaction was UNreasonable, because it's her job to be suspicious of people. So a guy walks in, puts a knife she (not being a knife person) can barely operate without almost hurting herself, into the collection basket. She reacts to this device that has a long, sharp blade on it, by calling over another guard, just in case this person who just put a long, sharp knife in her basket decides to get aggressive.
All of this happened at a government building. Now, without going into the political arena, can you off the top of your head think of ANY reason why security guards at checkpoints in government buildings might be, you know, on edge? Any reason at all? Hmmmmmm.....