To me, it all comes down to what the blood splatter expert has to say. It doesn’t look like it’s possible for an act of violence that produced that type of blood evidence (splatter, and quantity) would allow Gannon to be able to both walk to the truck, and also not leave blood inside.
They would have to say something very surprising for me to believe he didn’t make it home.
I firmly believe she didn’t plan on Gannon returning from that trip, but it appears she was forced to pivot.
I hate how the video doesn’t show him returning, but can’t get past the blood evidence at the same time.