Courts allowed the man’s assisted death after rejecting several appeals by his victims, who argued he had to face justice. The case even reached the Constitutional Court, which refused to deliberate on it, saying there has been no violation of fundamental rights.

Disgruntled former security guard Eugen Sabau (46) had shot three of his colleagues, including a woman, at the security services firm where he worked in the northeastern city of Tarragona, and then wounded a police officer while making his escape.

Sabau died at 6.30pm local time, according to a source from the Catalan regional government.

The prison authorities were unavailable for comment and Sabau’s lawyer did not comment.

Spain decriminalised euthanasia just over a year ago, preceding which helping someone to end their life had carried a jail term of up to 10 years. According to El Pais newspaper, in the year since the law came into force on June 25, at least 172 people had used the right to assisted death.

After barricading himself in a house with an arsenal of weapons, a tactical police unit stormed the place, shooting Sabau several times.

The “Gunslinger of Tarragona”, as the Spanish media referred to him, was left a tetraplegic, had one leg amputated, and the wounds caused chronic pain that could not be treated with painkillers due to his fragile state and which he said made his further existence unbearable.

A court in Tarragona ruled that it was Sabau’s fundamental right to request euthanasia, considering these circumstances.

(Reporting by Graham Keeley and Andrei Khalip; Editing by Bernadette Baum.)