From the little I know about the case this seems to be a bit of a Ceasar's Wife situation.

The guy was shot in the buttocks as he was running away, back across the border. He was not threatening the lives of the border guards and I think that the case rested on 'reasonable force'.

It looks as if it was only poor marksmanship that meant that the guy was not more seriously injured, or killed. It also appears that the two men were not aware that the guy was trying to smuggle in drugs. They then tried to cover up the shooting.

IMHO any law enforcement officer has to behave to a higher standard that might otherwise be the case, given the authority that they have. If they abuse that authority, as seems to be the case here, than they must be seen to be brought to book very publicly.