Let me ask you this, you are the police chief of anytown. You've seen years worth news from columbine, to various random bombings like the Boston marathon. You get a call from a highschool saying "We might have a bomb over here made by some muslim, get down here now".With that information what are you going to do?
Option 1:
Take it seriously: evacuate the school, send in the bomb squad to check and disarm a possible bomb and ask what the hell the kid was thinking. Then have money wasted on finding that the bomb is in deed a clock and having stuff thrown at you for detaining a suspect who turned out to be just some kid.
Option 2:
Or are going to ignore the call because you think it's a joke and risk an actual explosion going off. If your kid got killed in the blast, how would you feel if the police passed the call off as a prank? Plus then the news who be on the police for failing to stop a bomb, parents would be suing.
The police do not know every single detail for every situation as it is occurring. Everything has to be taken seriously until otherwise. It's the same reason why prank calling 911 is illegal, the same reason you don't walk to school with a prop gun and point it people, it's also the same reason you don't walk into a movie theater and scream fire. If you are fireman or a cop, you can't afford to make mistakes, second guess yourself, everything is serious business. We aren't psychics, we aren't god, we don't all the information or details.
also here is a real suit case bomb
just a clock right? or just a bomb? what do you think at first glance
Lets move on to the next group, the media which ranges from everything and anyone including Fox, CNN, RT, BBC, etc. All them have for years since 9/11 have reported on stories about evil muslim bombers for years and years. Plus there have been towns of movies and shows that have had muslim terrorists with bombs. Plus many of bombs in those movies and reportings are in suitcases just like that one. The media and movie industry created that stigma, not the police, not the government.
Which brings us to the next group, which is the school and the one who made the call. The ones who bought into the stigma in the first place and made the call. They should feel bad for buying into stereotypes.
The last person I want to mention is the kid. What happened to him is the product of stigma and reactions to real world events that have occurred. Yes he made a clock, but he built in a way that triggered everything in environment generated by stigma and past events that are still fresh. It would be taking a toy gun as a prank to columbine a few days after the shooting, or a flying a plane straight into pearl harbor right after the attack. Clearly there are better objects to house his creation than a suitcase, but he basically set him self up and the school took the bait.