Maybe the Stay-Puft DonutRoidBoy was afeared that Erik was going to beat him to death with the gun butt...
Samantha kept saying at the end of the interview that DonutRoidBoy was VERY aggressive, and that she thought Erik would have been shot even if he had followed the [multiple] commands and gotten down on the ground. They couldn't bag the interview fast enough after that...
You don't shoot three people in five years on the force without being aggressive...