There have been several bomb threats against schools in my area this week. All of them were hoaxes. A lot of people say that whoever calls in these threats is just some loser who wants attention. A similar issue happens in pharmacy robberies. The criminal will say they have a pipe bomb.
Has there ever been a threat somewhere that wasn’t a hoax? IIRC, every major terrorist attack in the USA was a surprise.
The question as posed in the title is different from the question as posed in the post. I don’t know the answer to the post. But this is my answer to the title: Until it has been determined to be a hoax, EVERY bomb threat is a real emergency.
The Cleveland Elementary School shooting in Stockton, CA in 1989 was preceded by a phone warning to the police.
In 1970 someone from the radical Weather Underground phoned in a warning to the New York Police Department main headquarters. A bomb went off less than 10 minutes later. A few months later the same thing happened at a courthouse on Long Island.
ISTR there were some other bombings by the radical left that were preceded by phoned warnings. And of course, the Irish Republican Army oftenphoned in warnings before setting off bombs.
What I was really asking was how many are not hoaxes. I see it happen several times every year, someone starts a panic by calling in a threat at a school, and it is always (at least in my area) a hoax. Usually around the time of finals, some a-hole does this hoping to get out of a test.
My WAG is (in the US) probably 99% or more are hoaxes.
http://www.wcsh6.com/story/news/local/biddeford-saco/2014/12/19/phone-threat-school-canceled--saco-thornton-academy/20628635/
Second multi-day school lockdown due to a bomb hoax this week. It used to be that if there was a threat, the school would be evacuated, searched, and everyone would go back when it was found to be safe.
Here in northwest Arkansas we seem to have a school bomb threat almost weekly. So far all hoaxes.
The problem is there are documented cases of bombs in [URL=“http://wthitv.com/2014/09/16/isp-bomb-tech-successfully-dismantles-two-homemade-bombs-each-with-50-yard-radius/”]or near schools. More than you hear about. So, even if it’s a prank and the bombs don’t cause any injuries, you have to take the threat seriously, because even a13-year old can build a working bomb.
Aside from community college dorks trying to get out of tests, bomb threats are also used for extortion, among other reasons.
Harvey’s Resort Hotel bombing, August 1980, was a real bomb, and a very sophisticated one, that blew up a substantial chunk of the building while bomb techs were trying to disarm it.
(ETA: That Wiki page includes a link to a directory of “Improvised explosive device bombings in the United States”. I didn’t poke through it to see how many of them were given advance warning, which is what the OP is asking about.)