“There was blood everywhere, the whole thing felt unreal,” a neighbour told the Aftonbladet newspaper.
The police were alerted at around 4pm on Sunday and arrived at the Alingsås apartment shortlythere and subsequently arrested a man in his forties.
One woman was stabbed to death, most likely with a knife or screwdriver, and children were also involved, police told the paper.
Officers have not yet found any motive for the crime, nor released any information about the extent of the injuries sustained by the three other victims.
All three injured people were taken to hospital and at least one is known to be a child. The woman was in her thirties and her family was not previously known by police.
Forensic investigators cordoned off the area into Sunday evening.
Police have labelled the crime as suspected murder, and have launched an preliminary investigation.