1x3 - The Walking Dead: The Oath

Karina is seen standing by one of the hospital's windows. Gale walks in and Karina tells her about the time she shot a man in cold blood and that when he was dying from the gunshot a little girl ran out from behind some bushes and started crying. She goes on to explain that she knew she would be the last one left in her group, as it would be her punishment for leaving that little girl alone. Gale tells her that she can offer her an alternative.