The bomb squad wasn't called because no one was under the impression that it was a real bomb, just that it LOOKED like a bomb. The police described it as a "hoax bomb." This was the law they referenced when he was arrested:
(a) A person commits an offense if the person knowingly manufactures, sells, purchases, transports, or possesses a hoax bomb with intent to use the hoax bomb to:
(1) make another believe that the hoax bomb is an explosive or incendiary device; or
(2) cause alarm or reaction of any type by an official of a public safety agency or volunteer agency organized to deal with emergencies.
(b) An offense under this section is a Class A misdemeanor.
http://codes.lp.findlaw.com/txstatutes/PE/10/46/46.08
The whole thing is idiotic but luckily he seems to have a bright future ahead of him once he can get out of Irving.