In an astounding twist of fate, the secret ex-husband of murdered Iraqi Iqbal Al-Hilli died in Mississippi on the very same day his former wife fatally was shot in the French Alps. Now French investigators, with the help of the FBI, want to know if it is more than a moribund coincidence.

On September 5, 2012, Iqbal Al-Hilli, 47, her husband Saad, 50, her mother Suhaila al-Allaf, 74, and French cyclist Sylvain Mollier, 45, were all killed with multiple gunshot wounds, including two finishing shots—a classic double tap —into each person’s forehead. The Al-Hilli family were all shot while they were inside their idling BMW station wagon, which was parked in a clearing along a lonely mining road. Mollier was shot outside the car by the driver’s side door. The family’s 7-year-old daughter, Zaeinab, was found alive outside the car, having been pistol-whipped and shot in the shoulder. Their other daughter, 4-year-old Zeena, was found eight hours after the murder, hiding under her dead mother’s corpse in the backseat. Meanwhile, in Mississippi, James Thompson, 60 —who had previously been married to Iqbal —died of an apparent heart attack just hours after the French quadruple murders.

The case has perplexed investigators from Day One. British and French detectives have chased multiple leads, including whether Mr. Al-Hilli was an Iraqi money smuggler for Sadaam Hussein, or whether Mollier’s work as a zirconium specialist at a nuclear fuel-development company played a role in the quadruple homicide.

Three arrests have been made, including Mr. Al-Hilli’s brother, who was thought to be in an inheritance dispute with the dead man, but all suspects were released due to lack of evidence. Witnesses also reported seeing a man on a motorcycle with a rare helmet in the area shortly before the bodies were discovered. A man fitting the description was detained, but later let go. There were also reports that a strangely dressed man visited the Al-Hilli family at their campground the day before they were murdered, and that Mr. Al-Hilli took a trip to Geneva, Switzerland, apparently to check on a secret Swiss bank account. None of the leads have been fruitful.

Now investigators are focused on the so-called secret life of Iqbal Al-Hilli, who apparently kept her first marriage hidden from her second husband. According to police records, Thompson, an American Harley-Davidson enthusiast and dentist, married Iqbal when she was a dental student in the United States in 1999 so she could obtain a green card to stay and work in the United States. The two reportedly shared a home, but not a bedroom, and Iqbal used the name Kelly among their freinds, according to media reports. After the minimum required time, they divorced and Iqbal moved to the United Kingdom. She met Saad a few years later and the two were married in 2003 after a three-month courtship.

The head of the French investigative team, Lieutenant-Colonel Benoit Vinnemann, told reporters in France that they were now focusing on Iqbal and her very secret life. “We have found out some surprising things about Iqbal al-Hilli and we still have received no explanation on certain questions,” he said.

In the United States, the FBI apparently requested to have Thompson’s body exhumed in early 2013 to verify his cause of death. At the time, his family, who had harbored the secret of the marriage of convenience, declined, stating that they didn’t want to get involved. Now, Thompson’s family said they may concede and allow the body to be exhumed to see if he really did die of a heart attack. Thompson’s daughter, Joy Martinolich, told The Daily Mail that her family always secretly suspected foul play. “If you wanted to kill somebody and get away with it you would do something that people would accept like a heart attack,” Martinolich told the British paper. “They would accept he was a bit overweight, that he had stress issues, he was pushing 60. It’s possible.”

Meanwhile, back in France, investigators are hoping the latest lead points them in the right direction to finally find out just who killed the Al-Hill family and the French cyclist, and, more importantly, why.