How Reaper terminators (Predator Missile) know when to engage targets?

At roughly 2pm in August 2007 four men were spotted on a hill top if Afghan. David Sullivan took control of a UAV Reaper. With out sending any soldiers to the hill to check out the figures Sullivan prepared to use a Predator missile fired from the reaper to neutralize these “Taliban soldiers” the UAV controller locked onto his target and the countdown begun. Before the deadly missile was fired they noticed the men stared doing push ups and sit ups. These men where not in fact Taliban they were friendly troops doing there daily work out but what they didn’t know is that they were less then a minute away from a friendly Predator missile. Are these robots just too deadly to use? Extreme research is going into these unmanned plains to see if they are just too deadly to be used with out a conform call from ground troops where the enemies position is