A Beechcraft 400A Beechjet, registered N826JH, ran off the end of runway 20L after landing at DeKalb-Peachtree Airport, GA (PDK) and then went through a fence before coming to rest near Dresden Drive. The airplane sustained substantial damage, and the airline transport rated pilot and co-pilot sustained serious injuries, while the two passengers sustained minor injuries. The pilot-in-command reported that presence of a Cessna airplane on final approach to runway 20R was a distraction. He felt rushed to land the airplane. He also reported that they used up 25 to 35 percent of the runway before touchdown, and after touchdown until coming to rest, the normal brakes were continuously applied, but the effectiveness was reported as being low. PROBABLE CAUSE: “The flight crew’s failure to obtain the proper airspeed for landing, which resulted in the airplane touching down too fast with inadequate runway remaining to stop and a subsequent runway overrun. Contributing to the accident were the failure of either pilot to call for a go-around and the flight crew’s poor crew resource management and lack of professionalism.”