As a reporter for The New York Times in 1971, Sheehan obtained the classified Pentagon Papers from Daniel Ellsberg. His series in the Times revealed a secret U.S. Department of Defense history of the Vietnam War and resulted in government attempts to halt publication.
Born on a farm in Holyoke, Massachusetts, Sheehan graduated from Harvard University with a B.A in 1958, served in the U.S. Army from 1959 to 1961 and was a reporter for UPI. He was awarded a non fiction Pulitzer Prize in 1989 for A Bright Shining Lie.
His wife, Susan Sheehan, was also awared a Pulitzer Prize in 1983 for Is There No Place on Earth for Me?