i think that bryan then struggled to get in to call for help. that he sat there. i think the perpetrator stood there and watched bryan die. >> reporter: and as for the location of the gun so close to dr. rein's own hand? so the killer must've put it there? >> correct. >> reporter: but were there any fingerprints on the gun? >> no. it looked like it had been wiped off with a solvent. >> reporter: so investigators now thought they knew how the murder occurred. but when it happened? that wasn't clear at all. friday night? saturday? it was an important question, of course. but just how important they might not have fully imagined just then. but there was no clear answer. in fact, the pathologist who conducted the autopsy left the space for time of death blank. remember, dr. rein returned home from a conference on friday evening, but his body wasn't found until sunday. investigators canvassed nearby farms. and? >> there was a neighbor that lived probably about a mile