How did stalin use the murder of sergei kirov to his own advantage?

He ordered all of the party members to be disarmed and held many trials to get rid of the old bolsheviks and conduct a purge in his party. People would be accused of participating in the Kirov assassination and would go through a show trial and be executed, and more often than not they had nothing to do with it actually. This is because it's believed that the assassination was done by someone from the party.