On July 29, 1962, four of Joe Strupp''s relatives were found shot to death in their South Dakota home.

The killer: Joe''s great-uncle, John Bowman.

The victims: Bowman, his wife, and their two teen-age sons.

The result: a shocking tale of simmering tensions, mixed motives, and deadly outcomes that still harbors a mystery-why did it happen?

When Joe first heard about the tragedy 20 years ago, he began a long and intense investigation into the family secret that revealed a tangled history of mental illness, alcoholism, and still-unanswered questions as to why this horrific crime occurred.

Why did a quiet, frustrated father with no history of violence kill his family in cold blood and then take his own life, leaving no note of explanation?

Why did the priest who administered last rites leave the church soon after?

Why was the killer allowed to leave a mental hospital after years of troubling incidents?

And why did Joe''s family keep it secret for 40 years?