Rep. Alexandria Ocasio-Cortez (D-N.Y.) ignited outrage Friday after she used a poem about the Holocaust to defend Rep. Ilhan Omar, the Minnesota Democrat who is embroiled in controversy herself.

What happened?

On Friday, President Donald Trump tweeted a video criticizing Omar for referring to the Islamic terrorists who attacked the United States on Sept. 11, 2001 as "some people who did something." The video spliced together Omar's controversial comments with footage from 9/11.

In response, Ocasio-Cortez urged members of Congress to condemn Trump for "dangerous targeting" of Omar.

"Members of Congress have a duty to respond to the President's explicit attack today.@IlhanMN's life is in danger. For our colleagues to be silent is to be complicit in the outright, dangerous targeting of a member of Congress," Ocasio-Cortez said.

With her tweet, Ocasio-Cortez included a picture of the famous poem from German theologian Martin Niemöller, who was imprisoned in Nazi concentration camps from 1938-1945 for opposing Hitler's Nazi regime. Niemöller only narrowly escaped execution.

The poem, which is mounted on a wall at the National Holocaust Museum in Washington, D.C., reads:

First they came for the socialists, and I did not speak out—
Because I was not a socialist.

Then they came for the trade unionists, and I did not speak out—
Because I was not a trade unionist.

Then they came for the Jews, and I did not speak out—
Because I was not a Jew.

Then they came for me—and there was no one left to speak for me.

What was the reaction?

Ben Shapiro — who is the biggest target of anti-Semitism online, according to the Anti-Defamation League — condemned Ocasio-Cortez's "deeply disturbing" comparison.

Others echoed Shapiro's sentiments: