2. The Hinterkaifek murders
“The Hinterkaifek murders took place in Germany in 1922. All six inhabitants of the farm were murdered with a mattock.
The residents of the farm reported strange occurrences, such as footprints leading towards the farm but not away from it. Some keys went missing, and the maid claimed the house was haunted.
After the bodies were found, it was obvious that someone had been living in the farmhouse for a few days after the murders were committed. So it looks like the killer snuck into the house before the murders and stayed there afterwards. No one was ever charged with the crime.” — MusicOfTheAinur
3. The assassination of Georgi Markov
“The assassination of Georgi Markov. On 7 September 1978, in London, UK. Markov walked across Waterloo Bridge spanning the River Thames, and waited at a bus stop to take a bus to his job at the BBC. He felt a slight sharp pain, as a bug bite or sting, on the back of his right thigh. He looked behind him and saw a man picking up an umbrella off the ground. The man hurriedly crossed to the other side of the street and got in a taxi which then drove away. He had been hit in the leg by a micro-engineered pellet containing ricin, fired from an umbrella. He died 4 days later. Speculation of KGB involvement has been suggested but the case remains unsolved.” — Mrdepressed90