I would imagine if an inmate killed a cop with his own gun then the inmate surely knew how to use the gun. So many police forces use Glocks and I imagine many a BG knows how a Glock functions.
I think if I was a cop transporting a prisoner he would be handcuffed behind his back and the cuffs zip tied to his waist. But I have never been a cop so what do I know. Safety for the cop must be top priority.
I do believe you kill a cop you get the needle and real soon rather than sit on death row for 20 years.