What We Know About Missing American Couple Last Seen at Brussels Airport

— -- Family members of a missing American couple said they are holding onto hope that the husband and wife will be found after last being seen at the Brussels airport shortly before Tuesday's deadly attacks.

The family of Stephanie and Justin Shults said the couple had been at the airport to drop off Stephanie Shults' mother when the bombs went off. Stephanie Shults' mother, Carolyn Moore, was visiting the couple at their home in Belgium and told her sister that the couple was sitting in chairs near security as she went through the line.

Moore's sister, Betty Gragg-Newsome, told ABC News today that Moore had made it through security and waved to the couple shortly before one of the bombs went off. Moore was thrown by the bomb blast, her sister told ABC News, and immediately after getting up, started to frantically look for her daughter and son-in-law.

Authorities are trying to assist Moore as she looks for the couple, but they haven't offered much information, Newsome said.

"Until we know Stephanie and Justin are safe, you’re just kind of in a knot. You’re worrying, hoping, hoping for the best, and worrying about the worst, trying not to let your emotions get ahead of you,” Newsome told ABC affiliate WTVQ. “We’re saying prayers, and putting their names on as many prayer chains as we can put them on, and just trying to be strong for each other."

Stephanie Shults works for Mars Inc. and the company posted a message on Facebook today asking for any information about the missing couple.

The couple had been living in Belgium but they have roots in Tennessee and Kentucky, where they grew up and went to school, according to Stephanie Shults' family.

Transylvania University, which Stephanie Shults attended as an undergraduate, posted a Facebook post about the alumna. Justin Shults grew up in Gatlinberg, Tennessee, and attended Vanderbilt University. He works for Clarcor Inc, which is based in Franklin, Tennessee, according to his Facebook page.