In my experience press accounts of police actions are about as reliable as press accounts of climbing accidents.

But if the report is to be believed, the narrative appears to suggest the robot was deployed to establish the exact location of the suspect within the building and secure his arrest without risking further bloodshed. Afterwards, once the coast was clear, the police got a warrant to search for evidence.

Pursuit of a person who is believed to be armed and dangerous is a well established "exigent circumstance" that justifies police entry into a home without a warrant.
It's true, I have a blog.