But he was an active shooter with a deadly weapon, not surrendering. If it had been a police sniper instead of a robot, that would have been no different and perhaps more familiar and expected?
If they had time to rig up an IED to the robot, and drive the sucker in there, use the camera to make sure he didn't have any hostages (they did that right?), and THEN detonate the bomb, it doesn't sound like the threat was all that imminent.
The FBI definition is "an individual actively engaged in killing or attempting to kill people in a confined and populated area".
He was cornered in a parking garage, not active.