http://www.aftonbladet.se/nyheter/krim/a/BaA97/terrormisstankt-gomde-sig-bland-tagpendlare
Swedish press is now reporting that the suspect is a 39 year old man from Uzbekistan that had shown sympathy towards ISIL. He was arrested in Märsta, around 30km north of where the attack was carried out. As it first happened there were also some reports I saw of a shooting by Fridhemsplan, but this has not been confirmed yet and seems to have been a false alarm.
I was on a southbound train by Solna station (around 4km north of the crime scene) when it happened, people seemed to be mostly handling it fine. There was initial shock but people didn't seem to get too phased. Traffic was absolute hell, though. Cops were absolutely everywhere during the day, a supermarket near where I live (20km from the scene) had policemen armed with automatic weapons standing guard at the entrance. Things seem to be calming down now, though.