If one or both of the brothers believed that your grandmother had witnessed something or had called the police on them, could be motive.
That's an excellent point. I just have a hard time seeing this as a random burglary gone bad or random murder. The method seems too violent to be entirely impersonal and nothing was taken, so what else could they want? If the grandparents had started making complaints to other neighbors or the police about the neighbor's drug usage, it could have made them angry and paranoid and lead to something like this.
It seems like they were targeted to me. It is possible someone could have searched for the paver as an afterthought (or the part of poor planning, which might indicate an unskilled killer such as someone who is covering their drug habit).
Is it possible that the grandmother maybe would have wanted to report something like drug dealing or use next door and the grandfather maybe said not to worry about it? If word got around about that then after the grandfather passed maybe they panicked thinking there was nothing to stop the grandmother from calling the police. Or it could have been done at that time to look like a shafted relative was angry about something will-related.
I am just having a hard time as seeing this as a purely random incident. A few questions for you, Maxa if you have a moment:
1. Based on the personalities of your grandparents, does the scenario I mentioned seem feasible or likely? Did one seem maybe a little more inclined to get angry and report illegal behavior than the other might have been?
I know this is going to be mostly opinion at this point, but I think it may help shed some light on what may have happened. For example, I know my grandmother would have made her unhappiness known to those involved and those nearby, however my grandparents on the other side of my family might have been more inclined to not say anything to keep the peace. Where did your grandmother and grandfather fall in this scale (so to speak)?
2. Did the druggies have any friends among your grandparent's other neighbors that you are aware of? Even people they might have casually spoke to off and on (like someone you might chat with while taking out the trash, etc)? Say someone who might have heard your grandmother or grandfather griping about doing something about the druggies next door that might have warned them or made them aware at some point?
3. I'm assuming not (or it would have been mentioned) but just to confirm, there were no police reports made by your grandparents or other neighbors regarding the illegal activity of the druggie neighbors?