Three people were injured in the shooting, which took place on Christmas Eve.
“We haven’t gone into the details yet, so I don’t know anything about his views on the suspicions,” said the man’s attorney, Per Althin, to the TT news agency.
The shots were fired shortly before midnight, just outside the Kungsgatan entrance to the casino in central Stockholm.
A man who earlier in the evening was denied entry to the casino returned, drew a firearm, and fired three shots toward the entrance.
Two female guests and a male security guard were hit by the bullets. One woman was hit in the arm, while the other was hit in the leg.
The third bullet hit the guard in the stomach, but the resulting injuries to the victims’ were minor.
An arrest warrant for the 23-year-old was issued a few days later on suspicions of attempted murder.
But it wasn’t until four and a half months later that police were able to locate the suspect.
“He was arrested without incident in the southern part of the county,” said Stockholm County police spokesperson Ulf Göranzon to TT.
No other suspects are being held in the case, according to police.
A preliminary interrogation is expected to take place on Wednesday, and police and prosecutors plan to hold an arraignment hearing for the 23-year-old as soon as possible.