[header] How to file criminal charges in california [title] Dial 911 to report a crime in progress. [step] Use 911 for emergencies. Call 911 after the fact if people are injured, or if you fear for your safety or think the person will come back. 
Try to remain calm, and give the operator a detailed description of where you are. [substeps] If anyone is injured, assess their condition as best you can so the 911 operator will know what level of response is required.