BOISE, Idaho (AP) _ Idaho Supreme Court Justice Allan G. Shepard died Saturday of complications following a heart attack two days before. He was 66.

Last week, Shepard stepped down as chief justice, but remained on the court. He cited his heavy work load as a reason for giving up his post.

Shepard joined the five-member Supreme Court in 1969. He suffered a heart attack in late 1987 that kept him off the bench for six weeks. He also was hospitalized early this year with chest pains.

Shepard served two terms as a Republican state legislator and held the state attorney general's post for six years. Phineas Newborn Jr.

MEMPHIS, Tenn. (AP) - Jazz pianist Phineas Newborn Jr. was found dead Friday at his home. He was 57.

The cause of death was not released. Irvin Salky, Newborn's agent, said X- rays six weeks ago showed a growth on one of Newborn's lungs but that Newborn skipped appointments for tests because he did not want to be hospitalized.

''In his prime, he was one of the three greatest jazz pianists of all time, right up there with Bud Powell and Art Tatum,'' said jazz critic Leonard Feather, a columnist for Downbeat magazine and the Los Angeles Times.

His albums included ''A World of Piano,'' ''The Newborn Touch,'' ''The Great Piano of Phineas'' and ''Piano Artistry of Phineas Newborn.'' Johnnie L. McHaynes

ST. LOUIS (AP) - Comedian Johnnie L. ''Mack'' McHaynes, half of the hefty comedy duo of Mack and Zack, died Thursday. He was 42. The cause of death was not been determined.

McHynes teamed with Zachary Scott Carey in the act that also was known at The Fat Boys from St. Louis, prior to Carey's death two years ago. Together, they weighed more than 750 pounds.

Mack and Zack made its television debut on the last episode of the ''Redd Foxx Comedy Show'' and later played hospital orderlies in the feature movie ''Nice Girls Don't Explode,'' in 1987. Jerry Anderson

MURFREESBORO, Tenn. (AP) - Former NFL player Jerry Anderson drowned Saturday after pulling two boys out of a rain-swollen river. He was 36.

''Mr. Anderson jumped in the water and managed to get the little boys out, but witnesses said he went under two or three times and about the fourth time, he didn't come back up,'' police Capt. Bill Todd said.

Todd said rescue workers pulled Anderson from the lake and took him to a local medical center, but efforts to revive him failed.

Five years ago, Anderson helped Tulsa, Okla., residents who were trapped in buildings and cars during a flood. He was honored by the city for his heroic actions.

Anderson, 36, grew up in Murfreesboro and attended Northeastern Oklahoma A& M Junior College, where he played football for two years before transferring to the University of Oklahoma. Anderson was a cornerback on the Sooners' 1975 national championship team.

Anderson played briefly in the NFL for Cincinnati and Tampa Bay. He also played in the Canadian Football League before his career was ended by a knee operation in 1982.