When one of these “events” explodes, they are better protected and have a better weapon ready right at the scene.
Most municipalities provide patrol officers with rifles now. That said rank/file patrol offciers are notoriously bad shots. SOP is for them to contain and call SWAT. Think if all the extra tax $ needed to equip and train for the scenario you suggest. Its just not necessary. Policing like many other jobs is dangerous. If youre not OK with that find another job.