A member of US diplomatic corps in Pakistan shot and killed 2 Pakistanis he said were trying to rob him. An already very anti-US public in Pakistan wants justice done for their slain countrymen; the US demands the diplomat be extradited because of his diplomatic immunity. The Pakistani civilian leadership, already with little popular respect, is trapped between the demands of an "ally" and the demands of its people. But if they don't let the American go, you can bet that US congressmen and the Fox News crowd will be screaming for Obama to get tough, and if that doesn't work, then direct intervention by US military to rescue the diplomat.
This could become really, really ugly.