Lived in the Hollywood Hills and this happened in the early 80's.
Crazy knocking at my door at 9PM. I go to answer the door and there's a lady there just hysterical, talking about "There's so much blood...". She looks normal and is dressed in clean clothing, so we let her in. She tells a story about seeing someone get stabbed. I call the police, and 2 uniformed LAPD officers arrive in 10 minutes. They take the lady away, and tell us that she has was reported missing, has a mental condition and lives up the street.
All good. 30 minutes later, another knock at the door. Two different cops this time, responding to the call. They have no idea who the other 2 cops were! Take our information and statements, description of the officers and the lady as well. Radio conversations back and forth ensue, and they really don't have any idea how any other cops could have picked her up, because they were given the call 40 minutes ago...