Dean Winslow has withdrawn as President Trump’s pick to head the military healthcare system, but he is not backing away from a comment about “insane” U.S. gun laws that derailed his nomination in the Senate.

The Senate Armed Services Committee put Winslow’s nomination on indefinite hold following a November confirmation hearing where the retired Air Force flight surgeon and Stanford University medical professor criticized public access to firearms in the wake of the Texas church shooting.

Winslow, who is a close friend of Defense Secretary Jim Mattis, announced his withdrawal in an op-ed Wednesday in the Washington Post. He said he had “blurted out what was in my heart,” has no regrets and remains opposed to the availability of what he called assault weapons.

“With a standard 30-round magazine, assault rifles are perfect for mass murder,” Winslow wrote. “Assault weapons in the United States are not being used to kill ‘bad guys’ in self-defense or to provide for a ‘well-regulated militia’ but for entertainment, mass murder and domestic terrorism. Is this really the intent of the Second Amendment?” he asked.

Pro-gun groups and Second Amendment advocates have criticized the use of the term assault weapon as a misleading term for semi-automatic rifles.

One of the weapons used in the Sutherland Springs, Texas, church shooting in November was a Ruger AR-556, which is a version of the AR-15 rifle. The AR-15, which itself is a semi-automatic version of the military’s M-16, is one of the most popular guns in America.

“As commander of an Air Force hospital in Baghdad during the surge, I have seen what these weapons do to human beings. The injuries are devastating,” Winslow said.

Firing them can be “a blast” for civilians but should be confined to licensed gun ranges, he said.

Winslow, who befriended Mattis at Stanford before he became defense secretary, said he was compelled to speak his mind during the confirmation hearing, even though the gun comment immediately drew the ire of Armed Services chairman Sen. John McCain, R-Ariz. He also acknowledged that his advocacy of therapeutic abortions in written committee documents played a roll in scuttling his nomination.

“As a devout Christian, a parent, a doctor and an American, I was deeply troubled by yet another loss of innocent lives, this time in the sanctity of a house of worship,” Winslow said.

He blamed the power of the gun lobby for forcing the withdrawal.

“As a citizen, I am saddened that our government has become so dominated by pro-gun lobbyists that an appointment such as mine — which has no responsibility for gun control — can be sidelined by a single sentence of informed, personal opinion. And that really is insane,” he said.