You really need to look at this as two separate incidents.
The police could end up at the wrong house for any number of reasons not all of which are malicious. There is no excuse for the actions of the police officer. The manner in which the SWAT team arrived at the house does not in any way change the culpability of an officer for their actions.
The prankster also has culpability here since they did what they did with the intent to cause harm and they should also be held accountable. To say the prankster is the root cause though is non-sense. The root cause of the man's death is the police's unprofessional handling of the incident.
The pranksters are the root cause, the reason this house came under the awareness of the cops at all.