Mollie was dead. The reward had a condition that she must be alive.
This is what the police website says:
"A large reward is being offered for information leading to the recovery of Mollie."
Iowa Department of Public Safety
Maybe they got if wrong and meant to say the "recovery of a living Mollie", but that is not what it says. Furthermore, if anyone he worked with suspected that he was involved, why would they assume she was dead? Police described her as a "missing person", and even Mollie's father said that she was still alive.