An American doctor who refused an evacuation from southern Gaza on Friday said he stayed behind in solidarity with colleagues who were unable to leave, calling on President Biden to help ensure the safety of medical workers treating patients impacted by the war.

“I have never in my career witnessed the level of atrocities and targeting of my medical colleagues as I have in Gaza,” Adam Hamawy, a former U.S. Army combat surgeon, said in a statement to The Washington Post on Saturday.