The former Texas School Book Depository, now the Sixth Floor Museum, overlooks Dealey Plaza in Dallas, through which the presidential motorcade was passing when John F. Kennedy was fatally shot. (LM Otero/AP)

Gary Mack, a former Texas television news producer whose interest in the death of President John F. Kennedy helped launch a museum at the Dallas warehouse where Kennedy’s assassin opened fire, died July 15 at 68.

The Sixth Floor Museum at Dealey Plaza announced the death but did not say where Mr. Mack died. The cause was cancer, his wife, Karin Strohbeck, told the Dallas Morning News.

Mr. Mack was born Lawrence Alan Dunkel in Oak Park, Ill., on July 29, 1946. He graduated from Arizona State University in 1969 and changed his name during his early career as a disc jockey.

He was an announcer, camera operator and news producer for KXAS-TV in Fort Worth and Dallas from 1981 to 1993. Privately, he was a student of Kennedy’s assassination.

Mr. Mack served as a consultant in the planning of “John F. Kennedy and the Memory of a Nation,” the exhibit that opened the Sixth Floor Museum in 1989. The museum is in the former Texas School Book Depository, and its sixth floor is the vantage point from which Lee Harvey Oswald fired at Kennedy as the president’s motorcade made its way through Dealey Plaza on Nov. 22, 1963.

Mr. Mack joined the museum staff in 1994 as an archivist and was named curator in 2000, becoming a name and face familiar to Kennedy history buffs. He also became the voice of the museum, providing the recorded narrations to exhibits and self-guided tours.

Mr. Mack had long professed at least the suspicion that Oswald did not act alone in the assassination. Yet he was active in debunking many conspiracy theories, and even those who were confirmed in the belief that Oswald was a lone actor revered Mr. Mack’s expertise.

“He was always a remarkable source of information about the case and a wise guide who helped me avoid the many investigative pitfalls and black holes of JFK’s murder,” Gerald Posner, author of the book “Case Closed,” in which he concluded that Oswald acted alone, told the Morning News.

Besides Mr. Mack’s wife, survivors include a son, a sister and two grandchildren, the Dallas paper reported.

— From staff and wire reports