It was an AC130, not a drone.

It was also a clusterfuck made possible by everyone involved:

1) The hospital had no Red Cross or Red Crescent symbol. Only an MSF flag.

2) Some of the AC130’s targeting and comms gear was malfunctioning though the crew was able to correctly locate the target manually. This is largely irrelevant because they found the target and engaged as ordered. However, it’s possible that hypothetical additional deconfliction and/or targeting updates could not have been processed because of the malfunctioning gear.

3) There are indications that the Afghanis deliberately misled ISAF into targeting the facility as they had an antagonistic and paranoid view of MSF.

4) There are indications that the ISAF commander failed to properly establish lines of communication and rules of engagement.

Like most things in life, and especially war, it is far from black and white.