I was a huge fan of some sort of crime of passion, that is, up until he was charged with first degree murder.
Something had to have indicated that Barry planned this, and I don’t think it’s something as small as him listening to forensic files in his car.
Knowing just what we know now, it does seem completely plausible that Barry discovered these communications and snapped. I think the timing also helps this argument (last communication is really close to the time Barry allegedly began the coverup).
But, it’s also possible that Suzanne had already made Barry aware of her intentions to leave him that weekend, and the timing is a coincidence.
We know from MG that Barry was supposedly acting strange at the job site that morning. If I recall, he left at around 11. That leaves over 3 hours until Suzanne’s last communication with JL, and the commencement of the coverup.
I think there’s a decent chance that Barry stopped on the way home, and perhaps made purchases that would indicate a premeditated crime.
They got to first degree murder somehow; hopefully we’ll know the answer tomorrow.