Hmm. Grenades. My suggestion would be to get a face shield, leather gloves, open them all, and drink them immediately.
Kidding aside, generally too much sugar in the prime, or it wasn't done brewing. Waaaay too much CO2 overpressurizing the bottle. Yeast basically eats sugar, pisses alchohol and farts carbon dioxide. If you added too much sugar to prime it, or it wasn't done brewing in the first place, then you can create the bottle bombs you have.
Least likely- the bottles you used weren't rated for pressurizing, but unless you're bottling in pickle jars or something, I doubt that's the case.
Never personally had that happen. Hydrometers do wonders for avoiding this- you always can tell exactly where you are at with the brewing process, and know when it's done brewing.
Cooling it below 50 or so (fridge's are usually in the high 30's) will stop the yeast process, and letting sit for two days or so would reduce pressure somewhat inside the bottles (absorbs CO2 into the beer). However, a few problems. Bottles still may explode anyway, and SWMBO will not like the mess in the fridge. Also, unless you want to wear protective gear every time you open the fridge, you may want to try something else. Cooler maybe? However, dumping in ice or dropping the bottles into ice water may set off your hand grenades too with physical jarring or thermal shock. Not the best option, really.
Opening them is the best bet. Gloves, eye protection, wrap the bottle in a towel, and very very carefully opening the bottles will defuse the grenades. At that point, you can either recap the bottles, dump it back into the fermenter to finish brewing out any sugar then re-prime and re-bottle, or just drink the warm beer.