No. More like a highly unfortunate industrial accident.
Wiki has a good reference page on “Ammonium Nitrate Disasters”, which highlights some of the bigger catastrophes, such as the Texas City Disaster and the Oppau Disaster of 1921.
I’m sure the responder might have thought it was a bomb, but it doesn’t mean that it was. Ammonium Nitrate does explode after all, especially considering there was a serious fire at the plant prior to the explosion.
Here’s the wiki page for one and all. Scary stuff.
True. That one ship of AN threw a 2-ton anchor more that 1.5 miles in Texas City. People in Galveston County thought they had been nuked.