I used to live in a bad part of town, so I have a few.
In the apartment complex we lived in, our downstairs neighbors were a military family. Mother, two kids, and- we thought- the Dad. Never heard much from then unless they were outside smoking and dropping ciggie butts all over the ground. One night we were woken by a commotion and police sirens. Peeking outside we could see a trail of blood running from under the stairs down the sidewalk. Apparently her ACTUAL husband had returned from deployment, found Faux Dad sleeping in his bed, and stabbed the mother after punching up the walls. She ran for help- leaving the two kids in the apartment.
Kids were fine, Dad was arrested, Mom moved everyone out shortly after.
Another day my husband called me from the parking lot. "You have GOT to come down here." I wandered down and came face to very large, bristly face with a pig head sitting in the back of a pickup truck. Someone in the complex had received a pig as a gift and dismembered it in the parking lot. They took the good parts to the gazebo where they proceeded to cook it in a large metal drum, stirring it with a two by four. When it was finished, everyone was invited to partake. There was much rejoicing.
One morning I was heading out to go to work and found a large quantity of blood splashed on the ground at the beginning of the sidewalk. It looked like someone had tossed it out of a bucket. The trail led around the corner. Being young and foolish I followed it, thinking someone might need help. It lead into the laundry room. I peeked in the doorway and the entire room was COVERED in blood. All over the machines, the floor, the ceiling. I backed out and went to work, and when I arrived I called the Management office. "Oh, someone hurt themselves in the laundry room," she said. "With a chainsaw?" I asked, but all she did was laugh. I never did find out what the heck happened.
Then there was the day I walked into the parking lot and about 70% percent of the cars had all the windows broken and the tires slashed. My car was spared, but there was a minefield of glass for the next couple of weeks since Management didn't want to clean it. The tenants organized a clean-up and got rid of the worst of it.
There were less dramatic instances, but it was weirdness almost weekly. I was glad when we moved.