“The argument seems to have been about a scratch on the attacker’s car,” said Ulf Palm, Västmanland police spokesman.
Initially police said they were seeking two suspected attackers. But it later emerged that one of the men seen running from the scene was in fact a witness who had set off in pursuit of the killer.
“We have now interviewed that person,” said Ulf Palm.
Police were called to the incident just before 8pm on Thursday. The 19-year-old who had been stabbed in the throat was rushed to hospital but his life could not be saved.
“We have committed all the resources we have available, including dog patrols, to finding the attacker,” said Palm.
Two knives were found at the scene.
The 28-year-old, who has been charged with murder in his absence, comes from Västerås and was previously known to police.