The suspect, who once won 1.2 million kronor in a lottery show broadcast live on TV4, is supected of killing a 29-year-old man outside the Magasinet restaurant in Upplands Väsby north of Stockholm in front of crowd of witnesses.
The 30-year-old made contact with the police just hours after the attack on Thursday and was arrested at an address in Upplands Väsby.
Police found the suspected murder weapon in a rubbish disposal room in the town.
“We believe the assailant threw the weapon away as he fled,” police spokesman Lars Lisberger told news agency TT.
Both the victim and the suspect were known to the police.
Police received a call at 1.20am and arrived together with emergency workers to find one man dead from gunshot injuries and a group of people who had witnessed the killing gathered outside the restaurant.
“Witnesses have been questioned overnight and it appears that it stems from some prior history between the men,” police spokesman Fredrik Ladenstedt said on Thursday.