In Episode 10, one of the first cases of humans versus diclonius is revealed as police investigate the murder of an entire family in a residential area. Upon entering the apartment, they discover a little girl they believe to be the lone survivor of the brutal murders. However, the girl is actually the killer herself, and kills two of the officers closest to her before being gunned down by the remaining officers. These officers are armed with the Glock 17.
The Glock 17 in particular was not present in the manga's version of events, as the style of gun in the scene is vague.