The brutal murder of a 16-year-old girl by her best friend has shocked local residents in northwestern Mexico, a region plagued by drug and gang related violence.

Facebook posts between the two 16-year-old classmates show the two had become very close friends, but the two had a serious falling out after one of the pair, Anel Baez, posted a picture of her friend Erandy Elizabeth Gutierrez in a 'compromising position' with a boy.

The two girls fought bitterly over the photo incident, but finally, Anel Baez invited her friend over to her home in an attempt to patch things up.

But, shortly after entering Baez's bedroom, Gutierrez asked to use the bathroom...but instead grabbed a knife from the kitchen and fatally stabbed her ex-friend a reported 65 times.

Pretending to be heartbroken over her friend's death, Gutierrez attended Baez's funeral...but by that time, cops had cracked the case, and the murderer was arrested during the funeral service.

As a minor, Gutierrez faces just seven years behind bars, but the family of deceased is pushing authorities to treat the killer as an adult, arguing that the 16 year-old should be held responsible for her heinous actions.