"There are people who were on the scene and witnessed this," Per Wetterlind of the Stockholm police told the TT news agency.
A forensics team was soon on the scene and the area was cordoned off. By Monday morning, no arrests have been made.
The shooting marks the second of its kind in the area in just two days, after a 22-year-old man was shot dead by Örby school on Friday night in what police labelled an "execution".
"It's not just a random killing. It is clear that the perpetrators are similar to their victim. You may interpret it as an execution, they were out to kill," Elizabeth Wernsten of the Stockholm police told the Expressen newspaper of Friday's shooting.
According to statistics from 2009, Stockholm's murder rate is in line with other capital cities, with an average of three murders per 100,000 inhabitants per annum. The figure is up from a low of 0.6/100,000 in the 1950s.