The two men are in their 60s and have known each other for many years.
The murder suspect lives in Nyköping and has represented the Sweden Democrats in local politics.
He was expelled from the party earlier this year.
The victim lived in Stockholm but was visiting Nyköping.
He disappeared at the turn of the month August-September last year, but after body parts were found in central Stockholm a couple of weeks later, the police began a preliminary investigation into suspected murder and the local politician soon became a suspect.
Looking together
During questioning, he denied for a long time that he had anything to do with the disappearance, but after the police found traces of blood and ignition particles in the man's apartment in Nyköping, he admitted in police questioning that he was holding the gun when the deadly shot fired.
According to the former local politician's version of events, they had jointly searched for a car key in the home, after which a gun was found.
The local politician claims that they disagreed, but that he did not know that the pistol was loaded when he picked it up in an upset state and a shot fired.
Saw no other option
After that, he saw no alternative but to get rid of the body.
It was the local politician's way of trying to get away and thus be able to keep his job and his political assignments, he says in interrogation.
The body parts were later found in watercourses in central Stockholm where the body was transported.
The suspect says in interrogation that he wanted to try to make it look like he pushed him there before he died.
The former local politician is now charged with murder, breach of the peace and serious gun crime.
In the second place, he is charged with causing another person's death.
The trial starts on June 22 in Stockholm District Court.
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The police found body parts in Stockholm and a former municipal politician in Nyköping is charged.
This is what has happened in the case of the suspected massacre.
Photo: SVT / montage