Syrian Gas Attack Connected to Bigger Conflict?

Another devastating report from the Middle East: some 40 children hit by a gas attack in Syria, with Assad’s government being blamed.
President Trump tweets Assad is an “animal,” but that Russia and Iran are responsible for backing him. And there’s a “big price to pay.”
Twelve hours later, missile strikes hit a Syrian air base, killing 14 including Iranians. Assad blames Israel, and Senator Lindsey Graham says Israel would have every right to do so “because Iran is very embedded in Syria.”
So, is there any evidence that the Syrian government is responsible for the gas attack? And what about the tensions between Israel, Syria and Iran?