originally discovered... in jellyfish. in clinical trials, prevagen has been shown to improve short-term memory. prevagen. the name to remember. next thi next this friday night, the family from iowa on vacation in mexico. the parents and two children discovered dead in the condo they had rented. here's abc's matt gutman. >> reporter: tonight, mexican authorities are investigating the mysterious culprit that killed that vacationing family from iowa. investigators say they found the sharps, kevin, amy, sterling and adriana in the condominium they rented at this seaside resort in tulum.