The Mcnair mudshark appears to be a towelhead (name Sahel Kazemi).

It's possible that this was an honor killing. If a male relative of Sahel discovered that she had been having relations with a chocolate-face, he would of had to take care of business in order to restore the family honor.

But a murder/suicide with her as the shooter is more likely. (Mcnair was shot multiple times and she was only shot once.) This makes sense because as a towelhead she must have felt especially ashamed for having become a mudshark. It probably hit her all at once ("what have I done?!").