LOUAI BESHARA/AFP/Getty Images
UN-Arab League envoy for Syria Kofi Annan (L) leaves his hotel with Syria's Deputy Foreign Minister Faisal al-Miqdad (R) on his way to a meeting with President Bashar al-Assad in Damascus on May 29, 2012. The former UN chief arrived in Syria on May 28, and expressed 'horror' at the Houla massacre of more than 100 people as he began a visit aimed at salvaging his battered peace plan.
Over the weekend, more than 100 civilians were massacred in Syria, most of them women and children and most shot at close range as the killers went house to house.
It's thought to be the work of pro-government militias. The Syrian regime has denied any role in the massacre, blaming the killings on so-called armed terrorists.
Today, Governments around the world expelled Syrian ambassadors and diplomats, an unusual, coordinated blow to Syrian President Bashar Assad's regime.
Andrew Tabler joins the show to explain more about the events over the weekend and the international reaction.
"It's a wakeup call for the international community," he told Madeleine Brand. "This country is descending into chaos... it presents big problems for the Obama administration."
Andrew Tabler, senior fellow for the Washington Institute. His new book is called, "In the Lion's Den: An Eyewitness Account of Washington's Battle with Syria."
The Associated Press contributed to this report.