Attacking with their fists and feet, men in dark suits and others are seen repeatedly kicking one woman as she lay curled on a sidewalk. Another person wrenches a woman's neck and throws her to the ground. A man with a bullhorn is repeatedly kicked in the face. In all, nine people were hurt.
"This isn't Turkey. This isn't a third-world country," McCain said on MSNBC.
Another video shared on social media Thursday showed Erdogan watching the melee unfold from the backseat of his vehicle. He later exits the vehicle and peers toward the chaos.
Turkey's embassy blamed the violence on demonstrators, saying they aggressively provoked Turkish-American citizens gathered to see Erdogan. The embassy alleged, without evidence, that the demonstrators were associated with the Kurdistan Workers' Party, or PKK, which has waged a three-decade-long insurgency against Turkey and is considered a terrorist group by the United States.
The violent capstone to Erdogan's visit spoke to the sky-high tensions between the U.S. and Turkey, NATO allies that have increasingly sparred over U.S. strategy toward defeating IS militants in Syria.
To Turkey's dismay, Trump has decided to arm Syrian Kurdish militants in the impending fight to retake the key city of Raqqa. Washington considers the Syrian Kurds an effective force against IS. Turkey sees them as a PKK extension and existential threat to Turkish sovereignty.
In its protest against Trump's decision, Turkey's foreign minister demanded Thursday that Trump dismiss the U.S. envoy in charge of the anti-IS coalition, Brett McGurk.
And Erdogan, speaking in Istanbul two days after meeting Trump, said he was putting Washington on notice that his forces won't hesitate to attack U.S.-backed Kurds if they threaten Turkey.
"We are already telling you in advance: Our rules of engagement give us this authority," Erdogan said. "We will take such a step and we won't discuss it or consult with anyone."
The Trump administration rushed to McGurk's defense.
State Department spokeswoman Heather Nauert said McGurk has "the full support and backing" of Trump and Secretary of State Rex Tillerson.
Still, Nauert sought to acknowledge Turkey's misgivings about terrorism by the PKK and other groups.
"We respect those concerns, and continue regular consultations with our NATO ally on this and other topics of mutual importance," Nauert said.