"The man was quite shocked at the response his activities had generated and most apologetic. We are currently working to identify the supplier of these devices and others which include an imitation shotgun.''
Mr Friend said while such items were not illegal, people need to use a "degree of common sense'' about where and how to use them.
"The member of the public who rang 111 died exactly the right thing and we would far prefer to deploy to an incident and find there is no threat than people think they are wasting police time and not call us and we fail to learn of a genuine incident.''
Mr Friend said police worked with the university to send out an alert email to everyone on campus to locate the trench coat-wearing man.
"We're very grateful for that person who saw something that didn't appear right and called 111.
"As in the case with all situations police treated the report seriously and responded accordingly, deploying armed staff to the area while also requiring a local primary school to activate their emergency plan and go into lock down.''