Vice President Joe Biden's son, Beau, has died of brain cancer, the vice president announced on Twitter late Saturday. Beau Biden was 46.

The announcement said Biden faced his death "with the same integrity, courage and strength he demonstrated every day of his life." Biden was the vice president's oldest son, born Feb. 3, 1969. He worked for the Justice Department in Philadelphia, was later a federal prosecutor in the U.S. attorney's office and was first elected attorney general of Delaware in 2006. He mounted a 2016 campaign for governor.

Biden joined the Delaware Army National Guard in 2003, earning the rank of major in the Judge Advocate General Corps. His unit was deployed to Iraq in 2008 and returned to the states nearly a year later. During his deployment, he turned over most of his work as attorney general to his deputy.

Biden was diagnosed with brain cancer in August 2013. He underwent treatment at Walter Reed National Military Medical Center in Bethesda, Maryland, in May, USA Today reported.

"The entire Biden family is saddened beyond words. We know that Beau's spirit will live on in all of us -- especially through his brave wife, Hallie, and two remarkable children, Natalie and Hunter," the Twitter announcement reads.

"Beau's life was defined by service to others. … Beau measured himself as a husband, father, son and brother. His absolute honor made him a role model for our family. His absolute honor made him a role model for our family. Beau embodied my father's saying that a parent knows success when his child turns out better than he did.

"In the words of the Biden family: Beau Biden was, quite simply, the finest man any of us have ever known."

Biden is survived by his wife, two children, father, stepmother, Jill, brother, Hunter, and half-sister, Ashley.

Funeral arrangements were not immediately released.