Former national security adviser John Bolton was so disturbed by the efforts to get the Ukrainians to investigate President Donald Trump’s political opponents that he called it a “drug deal,” former White House official Fiona Hill reportedly told Congress on Monday.

Hill, a former White House advisor on Russia, testified that Bolton told her he wanted no part in the effort that involved acting White House chief of staff Mick Mulvaney, a person in the room for Hill’s testimony told NBC News. Bolton also was said to have referred to Rudy Giuliani as a "hand grenade" that would "blow everybody up," according to the New York Times, which first reported details of Hill's testimony Monday.

Hill testified that Bolton, who was fired by Trump in September, told her to report the situation to the top lawyer at the National Security Council, John Eisenberg, according to the person in the room for Monday’s closed-door hearing.

Giuliani responded to the reported comments early Tuesday. "I always liked and respected John," he said. "I’m very disappointed that his bitterness drives him to attack a friend falsely and in a very personal way. It’s really ironic that John Bolton is calling anyone else a hand grenade. When John is described by many as an atomic bomb."