Do you know for a fact it's him? Smith and Brian are fairly common names. Either way, I have no idea if you should call. I hope a mod or one of the more experienced members can give you some advice about this. Maybe try asking in the general information section. I would say go for it but my biggest concern is that if you sound too suspicious, if he really is guilty he might try to cover it up even more.
I think it would be a good idea to let the other members here give suggestions for things you should ask -- details they really want to know about, etc. For my part, I agree with the questions you have in mind. It would help to have a more fleshed out scenario.
By the way, even in this case it's probably still a good idea to ask him first if he would be willing to talk to you. If he's not guilty or at least not directly, it could be traumatic for him and he might be sick of telling the same story over and over to LE.
I'm looking through that list and I think there could be a pattern there.
I would say contact a Mod with this inquiry and see if they can help. The mods/admins have stronger connections with cases than us standard users and they would be able to better go through the proper protocol much better. From what I remember in the forum rules, it's a violation for a WS member to request personal information. The thing is, I don't know if a phone call contact inquiry would be classified as a request for personal information. However, the person whom you are trying to contact could respond negatively, or not at all, or even lie, depending on their involvement with the case. If they are even connected.
Satch