Hello, these are some thoughts that I wanted to share with you about the killer's profile.
What if the killer was a friend of the victim? a school boyfriend?
First, in that case , it seems that Brendan was the last to be shot :
it does make it seem like these two murders involved an aspect of sadism and a desire to see the anguish of one victim while murdering the loved dad in front of his son . ( I recall the 2 victims were tied ).
According to my hypothesis, it was the son who was the main target of the killer. So, a very personal murder may be due to jealousy, envy and sadism. Brendan’s intelligence and academic success could have led to such hatred: let us not forget that he was blessed with a father who was very loving and devoted to his son.
According to my scenario, the friend phones Brendan to warn him that he will go home and put him in complete confidence . Once in the house, he pulls out his weapon and under threat forces them to attach each other: the victims do not believe in the worst and do not try to resist . Maybe even the killers are they two: 2 friends, 2 brothers, 1 couple father/son etc...
Let’s not forget that Brendan had just been selected for a gifted program: it may very well have stirred up hatred towards him and his father. It was well premeditated and very personal murders.
Maybe Brendan’s middle school is the way to solve this puzzle.