When I decock the pistol it fires. Luckily I was at the range when this happened and no injuries.  I  tried again and this happened.  What I need to replace? Thanks

My first thought would be the safety, but I would also check the hammer. The safety should have a little tab on the back that prevents the hammer from moving far enough forward to hit the firing pin. It bay be worn down or broken and not working. The spot on the hammer that hits the safety tab could be peened in as well. Unlikely, but possible.

Scary. I pull the safety lever and the firing pin while you are at it to check the surfaces. I'd check the safety like a CZ52 by putting a pencil down the bore and see if PF travel launches it rather than testing with live ammo.