Deaths in the news come and go like cars on a night highway. You see a name, age, what police say, and maybe you sigh and move on. But some deaths stick. Kaitlyn O’Hara’s sticks. She was killed three weeks ago on Route 70 near South Frontage Road in Cherry Hill trying to rescue a cat. She saw the animal, which was either frightened or injured, and pulled over. It was dark and overcast and freezing. As she proceeded, a car struck her. It was an accident, police said. She was 27 and lived in Medford. She was returning home from work as a veterinary nurse at the University of Pennsylvania.