"I am a witness, I am not a victim."
Translation:Ben şahidim, kurban değilim.
-(y)Im is the 1st person sing. copula (like I am)
-(I)m is the 1st person sing. possessive suffix.
If a word ends in a consonant, there is no way to tell them apart. There are a lot of suffixes like this in Turkish :) That being said, I did some research for you and discovered that "şahit" is a loanword from Arabic.