No one has yet been arrested and the act of violence is being investigated as aggravated assault.
The police do not want to go into how many perpetrators it may be about, but witness statements claim that four to five people may be involved.
How many of them were involved in the aggravated assault is unclear.
In the clip, Åsa Erikson, head of the preliminary investigation for the police youth group, talks about the importance of the bus' surveillance film from the attack.