Sen. Edward Moore "Ted" Kennedy died early Wednesday at his home in Hyannis Port, Mass. at the age of 77, CNN confirmed.

The Massachusetts senator was battling a brain tumor when he died. He was the second most senior member in the US Senate after President Pro Tempore Robert Byrd.

Kennedy had served in the US Senate since 1962.

In a press statement, California State Sen. Leland Yee (D-San Francisco) described him as "the moral standard for generations of lawmakers."

"For decades, Ted Kennedy, like his brothers, 'saw wrong and tried to right it, saw suffering and tried to heal it, saw war and tried to stop it,'" Yee wrote.

Kennedy, known as the "Lion of the Senate," played a crucial role in passing many important acts including the Civil Rights Act of 1964, the Americans with Disabilities Act in 1990 and the Family and Medical Leave Act in 1993.

House Speaker Nancy Pelosi, who also represents San Francisco's 8th district, called Kennedy "a great patriot" who had "a grand vision for America."

"Rooted in his deep patriotism, his abiding faith, and his deep concern for the least among us, no one has done more than Senator Kennedy to educate our children, care for our seniors, and ensure equality for all Americans," Pelosi wrote.

The most prominent member of the Kennedy family, he was the younger brother of the late President John Kennedy and Sen. Robert Kennedy both whom were assassinated in the 1960s.

Kennedy is survived by his second wife, Victoria Ann Reggie Kennedy and his five children from both his first and second marriages, according to CNN.