Rex Tillerson lived and died around the one real “Red Line” that exists for Donald Trump—his relationship to Russia.

Rex Tillerson was a surprise selection for secretary of State. His name was not among those suggested early on. In fact, he seemed to be a last moment decision, made based on a single factor: He had a good relationship with Vladimir Putin and had negotiated a huge contract between Russia and Exxon. Since taking office, Tillerson has attempted to be the model Trump employee. He’s left the offices of the State Department empty and done nothing about the dozens of open ambassadorships around the world. He’s negotiated no deals. He’s made no policy. He’s accepted humiliating public tongue-lashings from Trump—including having his own selection for deputy overridden.

None of that was enough to protect Tillerson when he dared suggest that not only was Russia behind a nerve agent attack in the UK, but that the United States would take action to protect their closest ally and NATO partner.

On Monday, British Prime Minister Theresa May issued a strong statement, indicting Russia for an attack on British soil that contaminated as many as 500 people with a nerve agent designed for chemical warfare. May gave the Russians until Tuesday to respond and promised that she would exact retribution for the Russian attack.

Shortly thereafter, Sarah Huckabee Sanders was confronted by reporters at the daily White House press conference. But she promised nothing in the way of action, and critically refused to say that Russia was involved in the poisoning of people in the UK.

REPORTER: So you're not saying that Russia was behind this act? SANDERS: Right now, we are standing with our UK ally. I think they're still working through even some of the details of that.

But a few hours later, Rex Tillerson didn’t attempt to hide the truth. On board a plane bound for Africa, Tillerson called the attack “a really egregious act,” said that the attack was clearly from Russia, and promised that the United States would act to defend its ally.

And just like that, he was gone.