Welles died of an apparent heart attack at his Bronx home last Tuesday, his son, Mark Welles, of Roslyn, N.Y. said on Sunday.
Welles retired in 2003 after more than 20 years as head of the B'nai B'rith Anti-Defamation League's Nazi-hunting operations. Finding ex-Nazis who had eluded post-World War II justice "was an overriding passion in his life," his son said.
"Basically he was determined to avenge for other people what they could not do for themselves," Mark Welles said.
Born Kurt Sauerquell in Vienna, Austria, on Sept. 18, 1927, Elliot Welles was among Jews rounded up early in the war and deported to Latvia. His mother, Anna, was one of a group singled out and executed in woods near Riga. He learned her fate when her clothes were returned two days later.
From Riga's ghetto, he was sent to the Stutthor concentration camp in Poland. As the war's end neared, he escaped during a forced march to another camp in Germany and made his way back to Vienna.
There he married Holocaust survivor Ceil Chaiken and they came to the United States in 1949. He based the name Welles on his own, which means "mineral wells" in German, and adopted the spelling as a nod toward actor Orson Welles, his son said.
In a series of jobs, Welles saved enough money to become part owner of the Lorelei, a restaurant in Yorkville, Manhattan's upper east side German enclave, which enabled him to establish German contacts that would help later in pursuing escaped Nazis.
Through the U.S. Office of Special Investigations, founded in 1979, he gained access to records in Germany that helped him locate the ex-Nazi SS officer who had ordered his mother's execution. The man was tried and convicted of several charges.
Although the sentence of two to three years in prison was mild, it motivated Welles to continue his quest for fugitives, his son said.
After Maikovskis fled to Germany in 1987, Welles pressured German authorities to try him again for his role in the mass arrest and execution of 200 Latvians. The trial began in 1990 and suspended in 1994 because of the 86-year-old defendant's poor health; he died two years later.