One thing: I have never fired a paintball gun, but could one become an accomplished shot with a regular firearm just by using a paintball gun? In other words, if he sights in his paintball gun, does that mean he can make the same kind of shots with a rifle shooting .223? I'm not sure. Would be interesting to know if your suspect also goes to the range.
We play a little paintball around the house with relatively inexpensive equipment. If I chose to purchase some of the more sophisticated models available, I'm certain it would improve my shooting.
Incidentally, my husband is an avid gun collector and hunter and I accompany him deer hunting several times a year. The very first time I went, he selected a gun for me and directed me to a specific stand. He had just sighted in the scope and I took great care not to jar it to effect alignment. I got a six point with one shot (and I was shaking so badly the whole shooting house was moving). One to two hundred yard shots are relatively easy even to an amateur with the right equipment.