Former national security adviser John Bolton exited the White House in September after a series of fundamental disputes with President Trump over foreign policy challenges in hotbed regions such as Iran, North Korea, and Afghanistan. But it seems Bolton was also concerned about another region: Ukraine.

In fact, Bolton was so alarmed by the nature of Trump’s phone call with Ukraine President Volodomyr Zelensky that he told an aide to alert White House lawyers about the potential conflict of interest, according to the New York Times.