Detective Kon and Barnelli jumped out of their car the moment it came to a stop and rushed into the school. They had clear concern on their face and both had their batons out and ready in case they needed to defend themselves or someone else.
It was incredibly difficult for police to deal with Users in city 4 since everyone, including the officers, were prohibited from carrying or using a gun regardless of the situation. It's no easy task retraining someone who can lift a car or create fire from their hands when you have to get up close and fight with your lesser strength.
Because of this difficulty, and often impossibility, police usually just ignore Users regardless of their actions, since they wouldn't be able to arrest them anyways. The few times an officer had managed to capture a User, the judge would often be bribed by whoever the User worked for and they would eventually be released without punishment.