Charlene Penn was a detective in the Seattle Police Department and also an Amazon.
In Seattle, the Amazons were breeding, leaving in their wake four dead men in two weeks with their hands and feet removed and an Amazonian symbol carved in their chest. Sam and Dean Winchester began investigating and met with Charlene Penn, the lead detective on the case.
However, Charlene was also an Amazon who informed Madeline that the Winchesters were on their trail. Madeline ordered the death of Sam and Dean.
As Sam left a meeting with Professor Morrison, Detective Penn confronted and attacked him, but Sam shot her in the chest and killed her.