I followed another case where a lake was a huge topic of contention. At this point in the case, I would be hesitant to rule out any point of entry to this crime. The picture of the entry with the guard had 3 vehicles entering at once and this was 2 days after the crime. Why not an officer at the gate querying anyone entering or leaving? Any innocent person would not protest such a tactic, right? As of Saturday, the house was still roped off with yellow tape including the pier and boat.
Do we know of any similar (minus a beheading) crimes being committed in the area? Rapes, break-ins, robberies, attempted assaults. . .
*sigh So many people had access to the lake, groundskeepers, housekeepers, etc. Again it seems the perp or perps are a good 2 to 3 days ahead of LE.
Also, thinking of Jessica Ridgeway, this could be a younger perp or perps deciding to kill someone just to see what it felt like and if they could get away with it.
I wholeheartedly agree with your statement "A local resident or someone already inside the boundary of the guarded gate could be the perp." This is why I feel any the people live there are fooling themselves if they believe it had to be an outsider.
I'm so sad that Mrs. Dermond is still missing on this Mother's Day. I hope she will be found soon for everyone's sake.