By Dana Bash and Ted Barrett, CNN
Washington (CNN) -- Daniel Inouye, a World War II veteran who received the Medal of Honor and represented Hawaii in the Senate for five decades, has died, his office announced Monday. He was 88.
He died of respiratory complications Monday evening shortly at Walter Reed National Military Medical Center, with his wife and son at his side.
Inouye was hospitalized last week and had undergone procedures to regulate his oxygen intake.
He won his ninth consecutive term in 2010 and was the second-longest-serving senator in the chamber's history, trailing only Sen. Robert Byrd of West Virginia. Inouye was a senator for all but three of Hawaii's 53 years as a state and had served as its first House member before that.
Senators of both parties took to the chamber floor Monday to mourn his death, and President Barack Obama described Inouye as "a true American hero."
"In Washington, he worked to strengthen our military, forge bipartisan consensus, and hold those of us in government accountable to the people we were elected to serve," Obama said in a statement. "But it was his incredible bravery during World War II -- including one heroic effort that cost him his arm but earned him the Medal of Honor -- that made Danny not just a colleague and a mentor, but someone revered by all of us lucky enough to know him. Our thoughts and prayers are with the Inouye family."