Dallas Police Officer Amber Guyger is claiming she shot her neighbor in self defense. In court this morning, Guyger broke down in tears as she began describing the night she shot and killed 26-year-old Botham Jean in his apartment. Guyger said she thought she was in her own apartment, which was one floor below where she entered. She said she mistook Jean for an intruder inside her apartment and didn't realize it was the wrong apartment until later. Prosecutors are arguing Guyger used excessive force.