a cloud darkened over the duenas family. when caseyrom high school in june -- >> i remember walking to where we would be seated and just seeing, my dad and mom along with other family members. but there was one spot missing. >> five months went by that we. as if those early police suspicious had faded away. but of course, we know better. don't we? >> coming up. mark duenas is in for a bitter shock. >> he was upset. like, are you kidding me? >> and what his family did next would surprise everyone. >> so this is never happened. >> yeah, like never! >> when dateline continues. ♪ breeze driftin' on... ♪ [coughing] ♪ ...by, you know how i feel. ♪ if you're tired of staring down your copd,... ♪ it's a new dawn, ♪ ♪ it's a new day... ♪ ...stop settling. ♪ ...and i'm feelin' good. ♪ start a new day with trelegy. no once-daily copd medicine has the power to treat copd in as many ways as trelegy. with three medicines in one inhaler, trelegy makes breathing easier for a full 24 hours, improves lung function, and helps prevent future flare-ups. tr