Has anyone posted any witness statements online? I looked and wasn't able to find any.
This is my own theory of the crime and I think it fits most with the evidence. It is well documented that cops often take minorities/indigent people on starlight tours, which is where they arrest someone for a low level crime like public intox or driving without a license and instead of taking them to jail, they dump em outside of city limits in some place that is fairly inhospitable. 99% of the time the person survives and doesn't say anything because they were caught doing something illegal and they are poor/minority/a criminal and they think they have no recourse.
What I think happened is that he took Felipe Santos out into the everglades and dumped him there, alive. Santos lived for a time before succumbing to the elements. When he got word that they hadn't heard from him, Calkins assumed that Santos fled back to Mexico or to some other city/state to avoid la migra. I think Calkins firmly believed the guy was alive at the end of their investigation of Santos' disappearance. Or at the very least, that the disappearance had nothing to do with him. After all, when he arrested Terrance, he did absolutely nothing to cover his tracks. He knows there were witnesses at the cemetary. He knew these phone calls and license plate traces were recorded. He knew his signature was going to be on the tow record. None of his actions speak to someone who is aware that there may be a criminal investigation of him.
Look at it this way, if Terrance Williams is found with a bullet in his skull, they are going to scrutinize his every move and find out Calkins lied to dispatch regarding the tow. He had just been through an investigation into his actions regarding Santos' disappearance. He KNEW they might look into his actions on the day that Williams was pulled over the way they did with Santos, so why wouldn't he take bigger steps to make sure there weren't traces of his involvement in this? Clean up his act from last time?
To me, the only explanation is that he legitimately did not know these two men would end up dead. When it became clear that they did die as a result of his actions, then he starts panicking and trying to cover his lies (he probably started suspecting something when he got a call from dispatch asking where the hell Terrance was). The sad thing is, if my hypothesis is true, both men lived for some time and could've been saved if he had just told the truth. :-(