The Department of Defense said Monday that it is opening an investigation into Arizona Sen. Mark Kelly, a retired Navy captain, in connection with a video he and other Democrats recorded urging members of the military and the intelligence community not to comply with illegal orders from President Donald Trump’s administration.

Defense Secretary Pete Hegseth said on X that the video, which set off a political firestorm last week, was “despicable, reckless, and false.”

“Five of the six individuals in that video do not fall under @DeptofWar jurisdiction (one is CIA and four are former military but not “retired”, so they are no longer subject to UCMJ). However, Mark Kelly (retired Navy Commander) is still subject to UCMJ—and he knows that,” he added.

A thorough review of allegations has been initiated to determine further actions, which could include recalling to active duty for court-martial proceedings or administrative measures, the Defense Department said.

Kelly, who spent more than two decades in the Navy as a pilot and retired as a captain, said on X that Hegseth’s post was the first he had heard of the investigation.

“If this is meant to intimidate me and other members of Congress from doing our jobs and holding this administration accountable, it won’t work,” he said. “I’ve given too much to this country to be silenced by bullies who care more about their own power than protecting the Constitution.”

Kelly’s fellow Arizona senator, Sen. Ruben Gallego, wrote in a post on X, “F— you and your investigation.” Gallego is also a Democrat.

Trump last week said on Truth Social that the Democratic lawmakers “should be arrested and put on trial,” accusing them of “seditious behavior” that, he said, could be “punishable by death.”

The next day, Trump said on conservative Brian Kilmeade’s radio show that he was “not threatening death” toward the members.

“I think they’re in serious trouble. I would say they’re in serious trouble. I’m not threatening death, but I think they’re in serious trouble,” Trump said. “In the old days, it was death. That was seditious behavior.”

The Democrats’ video was posted online on Tuesday as a direct appeal to members of the military and the intelligence community.

“This administration is pitting our uniformed military and intelligence community professionals against American citizens,” the lawmakers said in the video. “Like us, you all swore an oath to protect and defend this Constitution. Right now, the threats coming to our Constitution aren’t just coming from abroad but from right here at home. Our laws are clear. You can refuse illegal orders. You must refuse illegal orders. No one has to carry out orders that violate the law or our Constitution.”

In addition to Kelly, it featured Michigan Sen. Elissa Slotkin and Reps. Chris Deluzio of Pennsylvania, Maggie Goodlander of New Hampshire, Chrissy Houlahan of Pennsylvania and Jason Crow of Colorado. All are military veterans and former intelligence officials.

Multiple lawmakers in the video have said they have faced threats following Trump’s post.

“I’ve been through dangerous situations before, so it doesn’t change my feeling about speaking my mind,” Slotkin said Sunday during an interview ABC’s “This Week.” “But obviously, the president took issue with one sentence in a video and was calling for our death. I think that’s inappropriate, whether you’re a Democrat, Republican or an independent.”

Brennan Leach contributed.