Suicide murders were common in 18th century Denmark, and other primarily Lutheran European countries. At the time, Danes were far more religious and suicide was considered one of the greatest sins. But murder was punishable by death and it was a sin for which one could repent and therefore avoid being sent to Hell.

But eventually the authorities caught on, and in response established some of the harshest penalties for suicide murderers. But this did not work to dissuade suicidal individuals from committing murder. In fact, it was believed that the more one suffered before their death the closer they came to Heaven. 

As the number of suicide murders continued to grow in spite of the harsher penalties, Denmark eventually outlawed the death penalty in 1767. Eventually other countries followed their example.