I am puzzled. It is obvious that the friend, Duane Kulakofsky, is a POI at the very least and yet the police seem to have accepted that he did a disappearing act. This would be understandable if they had made a major effort to find him but I fail to see how that can be the case (unless Charley Project is seriously out of date) as finding him seems to be a matter of minutes on the web. He appears to be living in Omaha, Nebraska. I am always a bit cautious about records on the web as they may relate to past residences (before 2007 in this case) or someone with the same name; however that does not seem to be the case this time. All the various people search tools suggest there is only one Duane Kulakofsky in the USA and the individual in Omaha seems to be the right age at 39. That he is in (or has resided in) Omaha in recent years seems indisputable given the following;
A 2011 record of his achieving a taekwondo belt;
http://www.taekwondoomaha.com/news/?currentPage=22.
A 2014 record of a court case in Nebraska (interestingly labelled 'name change');
http://www.sarpy.com/attorney/documents/May-12-2014-Kelch-1.pdf
A July 2015 arrest record (from Oregon);
http://oregon.arrests.org/Arrests/Duane_Kulakofsky_23513217/. Although this is not from Nebraska it is definitely the same Duane Kulakofsky as in Omaha Nebraska as they match on initial of second name and DOB.
It seems likely that Duane originally came from Nebraska as he has an arrest record there going back to at least 1997 and there seems to be a Kulakofsky clan in the area. He also seems to have a long standing drug involvement which is still active (see the 2015 arrest). According to Radaris he has lived in several states over the years, including California (where he may have met Casey) and Blanca in Colorado - so I am pretty sure this is our boy.
Now.....if all this information is so readily to hand and he was arrested only 6 months ago - are LE doing anything to pursue him for further enquiries?