Be careful, this is hearsay and not evidence. Those people claim that he confessed to them, but there is a lot more context. Here is what the linked story says about the "he confessed" part:
> The investigation had gone cold until a jail inmate named Henry Cole, a man with a lengthy record, claimed that Mr. Williams confessed to him that he committed the murder while they were both locked up in jail. Cole directed police to Laura Asaro, a woman who had briefly dated Mr. Williams and had an extensive record of her own.
> Both of these individuals were known fabricators; neither revealed any information that was not either included in media accounts about the case or already known to the police. Their statements were inconsistent with their own prior statements, with each other’s accounts, and with the crime scene evidence, and none of the information they provided could be independently verified.