If it really were murder suicide (doubtful, IMO), the murderer would have had to manufacture some pretext to get the victim to go with him up to where they were found, and what story could he possibly come up with that his brother would believe? Especially when they were supposed to be on their way to the airport and they'd already missed one flight the day before! I imagine it would have been a tough job to get the other to agree to drive in the opposite direction so that they could... what, go watch the sunrise? I can't think of any plausible reasons he could have made up that the brother would believe and agree to.
Unless maybe he didn't even try to come up with a story and literally forced him at gunpoint. But from what I've heard about these two, I don't see that happening. Maybe one was just extremely distraught, and the other one realized the trip wasn't going to happen with him in that state, and they just drove around trying to calm him down until they ended up in the place they were found. But instead of calming down, things got worse instead.
It doesn't make any sense really.
Unless maybe he didn't even try to come up with a story and literally forced him at gunpoint. But from what I've heard about these two, I don't see that happening. Maybe one was just extremely distraught, and the other one realized the trip wasn't going to happen with him in that state, and they just drove around trying to calm him down until they ended up in the place they were found. But instead of calming down, things got worse instead.
It doesn't make any sense really.