Bihar: What triggered ruckus during Durga idol immersion in Munger?

One person was killed and several others were injured after a ruckus between police & crowd over Durga idol immersion in Bihar's Munger. Have a look at the video to know what triggered the clash between police and crowd and how the event turned violent. 
Several shots were fired in the incident between the two parties.
Watch the visuals here in this video.