Beau Biden in Walter Reed medical center

Beau Biden, the former Delaware attorney general and the vice president's eldest son, is undergoing treatment at Walter Reed National Military Medical Center near Washington.

The vice president's office confirmed Beau Biden, 46, has sought treatment at Walter Reed, but would not disclose his condition.

Biden, a member of the Delaware Army National Guard, has been largely absent from the public spotlight since August 2013, when he had a small lesion removed from his brain at the University of Texas M.D. Anderson Cancer Center in Houston.

Biden did not seek a third term as Delaware's top law enforcement official in November, saying he would seek the Delaware governor's office in 2016.

Biden has avoided media interviews and public events, offering very little public comment even during his final months as attorney general.

When Biden has attended public events in recent months, he has not offered public remarks and often departed quickly, like he did after briefly appearing in the Return Day parade in Georgetown this past November.

Biden also was in the audience at the Chase Center on Wilmington's Riverfront in January when his father spoke at a Martin Luther King Jr. breakfast hosted by the Organization of Minority Women. Beau Biden did not have a speaking role at the event, nor did he talk to press in attendance.

Biden sought treatment at M.D. Anderson after becoming weak and disoriented on a family vacation. In November of that year, three months after his procedure, doctors gave Biden a "clean bill of health," according to a statement issued by the hospital last year.

Few Delaware political insiders knew anything about Beau's condition late Tuesday.

"I'm very concerned that he's alright," said New Castle County Executive Tom Gordon, a friend and political ally of the Bidens. "That's all I care about. I've known him all his life. I'll be praying that he's fine."

Bob Gilligan, the Delaware Democratic National Committeeman and former House Speaker, said his "heart goes out to Beau and his family.

"My prayers and thoughts are with him," said Gilligan. "I'm not even interested in talking about politics at this time. I'm just hoping Beau is going to be OK and that's what's important. Everything else will take care of itself."

Timothy Mullaney, Biden's former chief of staff who was expected to help with a gubernatorial campaign, also only learned Tuesday evening about Biden's hospitalization at Walter Reed.

"I'll probably make some phone calls to try to figure out what's going on," Mullaney said.

Mullaney said he had spoken to Biden within the last month, and met with him several weeks ago.

Biden had been keeping a low profile "by design," Mullaney said, but he expected the former attorney general was serious about a campaign for governor. "I didn't anticipate we were going to do anything until this summer," Mullaney said. "Last time we talked he was fine, there was nothing that was going to stop him from running."

The 2013 incident was not Biden's first health scare.

Biden suffered what was described as a "mild stroke" in May 2010. Late last month, Grant & Eisenhofer, the Wilmington law firm that Biden joined after leaving office in January, said Biden was expanding his work on behalf of the firm's whistle-blower clients.

Stuart Grant, the firm's co-founder who made the announcement, did not immediately return a call on Tuesday.

Biden was first elected attorney general in 2006 and served two, four-year terms. He and his wife, Hallie, have two children and live in Greenville.

Contact Jonathan Starkey at (302) 983-6756, on Twitter @jwstarkey or at jstarkey@delawareonline.com.