There’s still no reason he should have had any of those bits of evidence still on his person though if he didn’t want to get caught.

My “I’d like it to be true” theory is that the guy is terminally ill anyhow, and escape vs. get caught later and have a platform due to the trial vs. be killed at the scene were all equally acceptable outcomes to him.

Hence the very meticulous planning and clear proficiency with the required steps to do the killing, yet (intentional?) sloppy drop of the phone and water bottle, and continuing to carry every bit of the evidence they could hope to find on him days later.