So the alternatives from Gaf are:
1) Leave ISIS alone (That was a weird one)
2) Boots on the ground against Iraq's wishes and basically becoming an invading force.
Reading the article, it looks like it was some really shitty luck and I feel awful for the people stuck in there. But again, bad things happens in war. Looks like the US forces were using a weapon to only hit a subsection of the building to only hit the sniper nest and the goal was to minimize collateral damage. It hitting the munitions cache was total bad luck, and dealing with an enemy who doesn't give one damn about the civilian population and willing to put weapons in places they know could kill hundreds of people.
My suggestion to anyone else is, what would you do instead? (Not knowing the result) If you were a military commander who has received a request from the Iraqi forces and intel to take out some snipers that were probably causing some serious damage to troops or assets on the front. You have a weapon to hit only a section of the building where they are at. The reports say there are little to no civilians in the area, as it seems like ISIS has pushed people out of their homes in the neighborhood. What do you do? Mind you, you are also working to liberate this city from ISIS, trying to make a push into the city with coalition forces.