[s2e10] The Hour Of Death -

The police department is compromised from the inside by an intern who uses his access to stalk and manipulate the lead detectives. Other Possible References

A series of brutal murders targeting the Wesen community in Portland sends them into a panic. The killer leaves behind a symbol—a "G"—that marks a particularly violent and extremist lineage of Grimms known as the Endezeichen . [S2E10] The Hour of Death

Ryan is not actually a Grimm. He is a Lebensauger (a Wesen) who suffers from extreme self-loathing. He obsessed over Grimm history to the point of killing his own kind to "prove" he belonged with the Grimms. Key Themes for a Paper/Analysis The police department is compromised from the inside

If you were referring to a different "[S2E10] The Hour of Death," there are a few other possibilities, though Grimm is the most prominent: Ryan is not actually a Grimm

The killer is revealed to be Ryan Smulson , the seemingly clumsy and eager police intern.

Analyze Ryan's psychological state. He is a Wesen who wants so desperately to be a "heroic" Grimm that he becomes a monster to his own people.