The youngest son of the late Sen. John McCain criticized Donald Trump’s political performance at Arlington National Cemetery on Tuesday and revealed that he has become a Democrat who plans to vote for Kamala Harris.

“It was a violation,” Jimmy McCain told CNN of Trump’s actions at Arlington, where several generations of his family are buried and where party political activities are prohibited.

McCain, who joined the Marine Corps at age 17 and has served in the military for 17 years, recently returned from a months-long deployment to a small base on the Jordan-Syria border.

“It just blows me away,” McCain said of Trump’s decision to use the cemetery as a backdrop for campaign content. “These men and women who are in the ground there, they don’t have a choice.”

Campaign activities are banned at U.S. military installations, including the Army’s Arlington National Cemetery, where an Army spokesman says a Trump campaign aide shoved an employee who tried to enforce the rules out of the cemetery. Ironically, John McCain apologized for violating the same rule with an ad for his failed 2000 presidential campaign that featured a clip of himself walking through the cemetery.

“I think anyone who’s spent a lot of time in uniform understands inherently that this isn’t about you,” Jimmy McCain told CNN. “It’s about these people who made the ultimate sacrifice on behalf of their country.”

McCain, who has been registered as an independent for several years, also said he registered as a Democrat weeks ago and will vote for Harris in November. He added that he would “get involved in any way I can” to help her campaign.

McCain is the son of Cindy McCain and brother of Meghan McCain, making him the first member of his family to turn his back on the GOP. He said the decision was partly motivated by Trump’s lack of respect for fallen soldiers.

His sister tweeted Tuesday that she will not support her brother’s decision to abandon the family’s conservative roots.

Jimmy McCain, who now serves as an intelligence officer in the 158th Infantry Regiment, also called Trump’s attacks on his father “not a war hero” because he was captured in Vietnam. He told CNN: “One thing about John McCain is he’s chosen to live a public life. So attacking him is not really outside his job description.”

“A lot of these men and women who served their country chose to do something bigger than themselves,” McCain said. “They woke up one morning, they signed on the dotted line, they raised their right hand, and they chose to serve their country. And that’s an experience that Donald Trump hasn’t had. And I think that’s something he thinks about a lot.”