The Washington D.C Metro P.D. switched to the Glock in 1989 and was supported by officers and their FOP.
Almost immediately they began to shoot themselves and each other. In the decade after adopting the pistol there were more than 120 accidental discharges which resulted in 19 serious officer injuries. Police mistakenly wounded nine DC citizens and killed one. This resulted in city government paying out millions in damages however they did not blame the guns. After investigating the incidents they found it related back to three factors.
The department, responding to turnover and rising crime, hired 1500 new officers in just 18 months. It then failed to train many of the rookies. In many cases the rookies only received three days range time instead of the normal ten. They simply rushed them through to meet the numbers they needed. The final factor is that they issued the easy to fire Glock in the hands of every one of the untrained officers without further thought.
The pistol is an excellent first gun as it is simple and light, but without the training to go with it a new shooter is probably more likely to make a dangerous mistake with it as compared to other firearms.