Raymond N. Nelson, a well known Capitol Hill staffer for more than two decades, was discovered brutally beaten to death yesterday in his Northeast Washington apartment.

Nelson, 59, was found by his roommate at 701 Quincy St. NE, about 7:30 a.m., D.C. police said. Police said he died of head injuries. Police said they have no motive in the killing and refused to say what weapon was used in the beating.

Nelson's death shocked neighbors, friends and Capitol Hill colleagues. "I deeply regret this horrible, senseless tragedy," said Sen. Clairborne Pell (D-R.I.) for whom Nelson had worked as an adminsitrative assistant for 13 years. "Ray Nelson was a dear and old friend of my wife and me, as well as an associate who worked with me for many years. I grieve with and for his wife and children."

Nelson worked as Pell's administrative assistant until 1974 when he joined the staff of the Senate Rules Committee. "He was the person mainly in charge of room space allocation in the Senate Building," said John B. Childers, deputy staff director for the committee."He probably knew more people in the Senate than any single person and more people knew him."

"He was very full of love, very generous, very full of life and vitality," said his daughter-in-law, Vicky, who was at the family's Bethesda home yesterday. "He was always looking for the good things in life."

Neighbors said Nelson and his wife Shirley, had been separated for several years. The couple had three children -- David, Rebecca and Marc.

Even though the couple was separated, neighbors said Nelson was often seen working in the yard and walking the dog.

Nelson, whom friends and colleagues described as a dapper dresser with a penchant for hats he wore cocked to one side, was a native of Providence, R.I.

A 1939 high school graduate, Nelson was an aviation machinist in the U.S. Navy during World War II. In 1946, he joined the Providence Journal, where he was a reporter and later became chief of the bureau in Warwick, the paper's largest suburban bureau.

He became campaign press secretary for Pell in 1960. When Pell came to Washington in January 1961, Nelson became his administrative assistant.