I have to admit I also feel the gun came first. From TA's shower poses, positions of his fists on his chest and the look on his face, I believe he was being threatened with the gun. The first bullet hit him in the head (Perfect position sitting on floor in shower). One bullet may not have fit properly in the chamber and misfired, allowing Travis time to get to the sink, then she started stabbing him in the back. He turned to fight her off, then she stabbed him in the heart, he fell to the floor and started crawling down the hall, when she climbed on his back and slit his throat.
I feel her accounting of the ninjas to Det. Flores, was a close accounting of what Jodi actually did, hearling a gunshot first, including mentioning a misfire and Travis crawling on all 4's, therefore, I believe the gunshot came first. By switching weapons, it is premeditation.