because of mark. and so are we. the world lost a good man. somebody who was resolute, always knew that the difference between right and wrong and would fight for that. reporter: now, special prosecutors toby and bill along with a multi-agency task force were fighting for mark. searching for his killer, but not coming up with easy answers. because he was so close to his friend and employee, d.a. mike mcclelland had to bow out of the investigation. they were doing what they could. opening their files to investigators. anything that anyone can think of they are looking for. reporter: checks on his personal background went nowhere so they continued to look at his professional cases. from 30 years ago to the week before. but it was slow going. how do you sift it was not this person but it could be this person. you are seeing if they are locked up.
the first number corresponded to a tip from early in the hasse case, the tipster claimed to have overheard two men in a bar saying they d killed mark hasse. that meant the tip came from william s computer. a follow-up computer search also revealed williams had searched several how-to websites. one of the websites was how to throw the police off an investigation by sending in fake tips. reporter: the second number on that scrap paper was even more important, because it turned out to be the real thing. it matched back to that computer message that gave details about the hasse murder weapon and also threatened more killings. so we knew right then that that tip that had come into the command post was sent by eric williams. and we knew right then we were gonna be able to put eric williams in jail. reporter: he was arrested, not for murder, but for making a terrorist threat about killing a judge.
this investigation suggested to you that you re a person of interest in the investigation? no. reporter: after the denial, his sympathies. my heart-felt condolences go out to both the mclelland family and the hasse family because they were in public office doing the right thing and for some reason, that we re not aware of, they ve paid the ultimate price for that. reporter: williams was known to be a bit of an odd duck, but a murder suspect? it seems so farfetched that a justice of the peace, a man who had served his county not only as an attorney, a judge, but also as a as a deputy sheriff, would then suddenly turn into this serial killer. uh-huh. yeah, no no one wants to think a lawyer would do that, a person who was a public servant would do that. reporter: in fact, he was among the many people investigators had already looked at after the hasse murder. what was his alibi at the time? he said he had been at home either caring for his wife or his in-laws down th
you heard the word, guilty. it s a gift. it was a gift for us. it s probably a gift for everybody else because i don t believe that this would ve stopped at the end of these killings. reporter: there s a sad postscript to this case that raises a painful question. could williams have been stopped after the hasse murder and before the mclelland s? did they have to die? in a haunting irony, mike mclelland always thought williams was likely the killer. he certainly suspected it was eric williams after mark hasse was shot. and he made no secret of what his opinion was. and i had numerous conversations where he said, bill, it s eric williams. reporter: williams was one of a handful of possible suspects, early on in the hasse case, but there was no evidence on him. and even with his conviction for theft, he d had a good reputation. of course eric s name came up in the discussions. but if you can t prove it, then it doesn t matter. reporter: and now this former justice of the peac
taurus, but with no license plate. we were going around looking for the car. i don t think i have noticed how many silver, light colored four-door sedans there are. reporter: and even though the killer attacked in the morning rush, he covered up. one of the witnesses described him as wearing a hoodie. that was black. and covered their face. and then, another person who saw him from a distance said, you know, all black. dark clothing. reporter: but there was something more. a witness in a garage right across the street heard the victim s last words. mark said, no, no, i m sorry. and that was after a little bit of a shoving match. reporter: did that tell you that these two knew each other? that seemed personal to me. reporter: no weapon was found at the scene and no shell casings either. did that tell you anything that