Call a drone strike on the Syrian government. Since their internet is down, the operation can stay hidden for ~10 years.

The Syrian government has begun attacking its civilians, and has shut down the internet in Syria to cover-up this fact. Unfortunately for them, this also means that an attack on the Syrian government itself won't be noticed until after the internet there is reconnected, and even then there will be no documentation of how the attack happened. Therefore, a drone strike on the head of the Syrian government should be sufficient to stop the needless murdering of innocent individuals, women, children, and our brothers in another land. In addition, the unique nature of this situation means the strike could remain classified for at least 10 years, so no one would be able to blame the United States until so far into the future that it wouldn't matter anyways.