On 4 March 1961, a mass shooting occurred at Thorild School in central Kungälv, Västra Götaland, Sweden, in which a gunman shot and killed one person, Per Håkan Altvall, and injured six others.

Andersson then went to get his gun, came back and started shooting, killing Altvall before escaping and hiding in the Fontin forest.

The chase for Andersson was the largest police activity in west Sweden to date, involving a total of 50 policemen plus dogs.

This event led to the first proposal to the government to investigate the effects of media violence, and the then-popular radio show "Tidsspegeln" (Mirror of Time) held a debate about "ideals and heroes for the youth" with the headline "Can we blame Cartwrights".

A 1995 article in Swedish newspaper Dagens Nyheter reported that Andersson was considered mentally unbalanced, partly because of the effects of alcohol, at the time of the shooting, and sentenced to closed psychiatric treatment.