It was probably the zombies who broke the machine.
Alarm will trigger regardless of who broke stuff. Avoid buildings with alarms around zombies.
Or just acquire a gas/PBA mask, a non-metallic weapon and bash the riot bots down. They can’t do anything to you if you have good environmental protection on eyes and mouth and are using a weapon that doesn’t contain any metal (unless that weapon is an unarmed weapon or your fist).