Ruth Mills

In a parallel universe, Ruth Mills was a human whose father, Eric Vollmer, died in the Deep-sea Energy Exploration Project base in 2039. The Doctor promised he would take care of his daughter. Ruth discovered 27 years later that it was the Doctor who killed Vollmer. She shot the Doctor, making him regenerate into a new incarnation, then planned to keep shooting him until he remained dead. (AUDIO: Full Fathom Five)