putting water on an ammonium nitrate fire seems to be the real tragedy...

http://www.ehow.com/info_8262206_happens-add-ammonium-nitrate-water.html#ixzz2Qvt3Shf4

However, when aqueous or dissolved ammonium nitrate is heated, the solution breaks down to release nitrous oxide, or laughing gas.
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i just lock, load, and regret. - jamesn