Police said a six-year-old girl was sexually assaulted in a stairwell of an apartment building on 318 Patricia Avenue at approximately 7 p.m. Friday. (Colin Butler)

Waterloo Regional Police have arrested a 27-year-old Kitchener man after responding to an assault on Charles Street East. 

Police say the man was found with a rock placed in a sock which was used as a weapon. 

Investigators believe the man used a similar weapon in another recent incident involving an assault. 

The man has been charged with assault with a weapon and assault causing bodily harm. 

A second 22-year-old man was also charged with assault and breach of probation at the scene.

Both men are being held until they appear in court.