"Before I kill myself, I better put on my seat belt because muh safety."
Look at his sleeve. It's covering his entire wrist. If he ever had his hand near his head, his sleeve would be farther down his wrist.
The killer grabbed his sleeve with his right hand as he placed the gun using his left hand. The sleeve was pulled down over the wrist during the plant.
Yes, lots of extra fabric on the sleeve ABOVE the elbow. Pretty taught below the elbow though. His sleeve would not be that low on his hand if his arm was bent near his temple.
Most wear their watch on their non-writing hand to save the band from getting worn out while writing.