When two special needs students vanish from a Florida middle school, delayed search efforts yield tragic consequences.

The FBI identifies a serial predator as a potential suspect after nearly 20 years in this episode of Last Seen Alive.

Music Thanks for listening to Last Seen Alive.

I'm your host, Leah, crime analyst by day and true crime storyteller by night.

And as always, I'm your co-host, Scott.

A quick heads up. This episode contains discussion of crimes against children. It also contains

mention of sexual assault. We won't go into explicit detail, but still, please listen with care.

Brian Hayes and Mark Degner were last seen alive on February 10, 2005.

They were 13 and 12 years old at the time, respectively, and both lived in Jacksonville, Florida.

With nearly a million citizens, Jacksonville is Florida's largest city, and in such a large city,

there are are unfortunately,

hundreds of children who've gone missing over the years. However, Brian and Mark's case is fairly

unique not only because they were among the minority of missing children who weren't found,

but also in that theirs was a double disappearance. The boys vanished together, and no trace of either of them

has been found since. Mark and Brian were best friends. They were both students at a middle school

located on Norman E. Thaggard Boulevard on the city's west side. They were in the same

special education classes together and had really bonded with one another. Both boys had,

of course, been placed in the classes because of special educational needs, which was one of the

things they shared in common. According to a Newsweek article on this case, Brian, who had not had an

easy start to life, had developmental delays that meant his physical age didn't match his mental age. Chronologically,

he was 12, but psychologically, he was somewhere between the ages of 7 to 9. He had also been

diagnosed with bipolar disorder for which he took daily medication. By the time of his disappearance,

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