The brother of the victim stabbed to death the 30-year-old brother of the alleged gunman in a disputed dating back to 1997, Saint Gallen cantonal police said, according to a report from the SDA news agency.
The man suspected in Friday’s shooting, a Serb of Albanian origin now 51, was seriously injured in that attack 17 years ago, which occurred in broad daylight in the town of Walenstadt, SDA said, citing media reports.
The knife-wielding attacker turned himself into police and was subsequently convicted of murder, the news agency said.
The suspect in Friday’s event is alleged to have shot the victim, a Swiss citizen of Albanian origin identified by media as an 18-year-old, several times in the El-Hidaje mosque, located in an industrial neighbourhood in the west part of Saint Gallen.
He subsequently gave himself up to police and admitted his crime before the local prosecutor.
Cantonal police said they would not be commenting any further on the investigation, which is now in the hands of the prosecutor’s office.
Meanwhile, a right-wing MP from the canton of Valais has stoked controversy by tweeting "we need more of them" in reference to a media article about the mosque shooting.
The comment from Jean-Luc Addor, member of the Swiss People's Party, "is on the border of illegality", Martine Brunschwig Graf, president of the federal commission against racism, was quoted as saying by the 20 Minuten newspaper.
Hisham Maizar, president of the federation of Islamic umbrella organizations in Switzerland, told the newspaper the group is considering legal action against the politician.
The fact that such an act (the shooting) happened in a mosque is a huge shock for us Muslims," Maizar said.
"When a person like Addor then makes jokes about it, this must not remain unanswered."
On en redemande ! http://t.co/rcdBnznvbK
— Jean-Luc Addor (@udcvr64) August 22, 2014