Master Chief Boatwain's Mate Sam A. Novello, 56, who was shot and killed April 16 by alleged leftist terrorists in an ambush outside his home in Istanbul, Turkey, was a deep seadiver for 27 of his 37 years of service in the U.S. Navy.

Turkish police said Ali Sami Baydar, a Turkish citizen and a friend of Chief Novello, also was killed in the ambush. Police said two of the three attackers, all members of the underground Marxist-Leninist Armed Propaganda Union, were captured. One attacker was killed in a gun battle with police, following the shooting.

Chief Novello spent 15 of the last 20 years in Turkey. His first assignment there was in 1961 as a diving and salvage adviser to the Turkish navy. In 1965, he returned to Turkey and spent the next nine years as the senior naval representative in Istanbul.

Since 1976, he had been stationed in Turkey as an adviser to the Turkish navy.

Chief Novello, who was born in Erie, Pa., received a number of superior service awards from the U.S. and Turkish governments.

He was stationed in Washington at the Naval School of Diving and Salvage and at the Defense Language Institute during the late 1950's and early and mid-1960s. He returned here in 1974-75 as chief master at arms and transportation officer at the Naval Diving School. He was a former resident of Suitland.

During World War II, Chief Novello served aboard the destroyer USS Gransevoolt in the Pacific theater.

Survivors include a sister, Helen Damico of Erie, and two brothers, John, also of Erie, and Joseph, of Johnson City, Tenn.