Seven men between the ages of 17 and 21 have previously been arrested for the fatal shooting.
Two are suspected of probable cause for murder and the others are reasonably suspected of aiding and abetting murder, the police said on Saturday.
The eighth man is also reasonably suspected of aiding and abetting murder.
He is in his 20s and was arrested on Sunday after questioning, local media reports.
All suspects deny involvement in the murder, writes Smålandsposten.
Answer on Monday about detention
By Tuesday at the latest, the prosecutor must decide whether the detainees should be requested to be detained.
- On Monday, I will take a position on how we should proceed with the suspects, says chamber prosecutor Emma Berge to Smålandsposten.
Can be a deal
One of the police's theories is that the murder is a settlement within criminal groups and the regional task force participated in the arrests.
The murdered 28-year-old was already known to the police and his contacts and conflicts were well known.
This allowed the police to quickly call in suspected killers and possible motives, according to the newspaper.