The man, 26, was shot in the head in a shoot-out with police, receiving life-threatening injuries. He is still in critical condition.
At least two other robbers escaped from the shopping mall in a getaway vehicle.
Four people were caught and arrested at different times and locations on Friday night with the last arrest taking place at 1.26am in Huddinge, a suburb in south Stockholm.
Police searched for more suspected perpetrators overnight.
Late on Friday night police cordoned off an area by the Heron City shopping mall in south Stockholm, newspaper Dagens Nyheter reported.
According to one witness, there were more than 20 police cars there, with officers armed with automatic weapons and wearing bulletproof vests and hoods.
One officer confirmed that they were looking for the robbers who had escaped from the scene in Södertälje.
The armed robbery took place around 11.30am on Friday.
Arriving at the scene police engaged in a shoot-out with four masked robbers, injuring one.
Three others escaped in a silver-coloured Audi, which was later found. The robbers likely switched to another car.
A witness told the TT news agency that the incident left bystanders shocked and in tears.
"I was on the escalator, about 10 or 15 meters away and heard people screaming. The crashed through the display and started taking things," the witness said.
"It was so brutal. People were terrified."
The man who was shot in the head is a 26-year-old from Norsborg, south of Stockholm. His family is with him at the hospital.
Due to his condition he has been formally arrested but not detained.
According to media reports, the four detainees are between 19 and 22 years old.
A 22-year-old man is suspected of violent robbery, a 19-year-old man is suspected of preparing a violent robbery and a 21-year-old woman is suspected of assisting a violent robbery. Another 21-year-old man is suspected of protecting a criminal.
TT/The Local/nr Follow The Local on Twitter