>>sot tony ribera/former s.f. police chief 47-53 --every time an officer puts on their uniform and hits the streets they know there's a potential threat out there. >> reporter: former san francisco police chief tony ribera says the fear factor coupled with strategies for self defense are something all law enforcement officers deal with on a regular basis, but he says the murder of police officers in dallas heightens the concern, especially when there are direct threats. >>i think officers need to very very cautious, aware of their surroundings and take due diligence in terms of ensuring they don't take unnecessary risk >> reporter: 7 francisco police as their offices on alert fans already writing to to a car in most cases. --seven francisco police say that their offices all ali on alert and are writing to- to a car in most cases. >> grant:there is much more ahead at five. a former san mateo police officer facing numerous sexual assault charges tonight. when he allegeldly attacked his victims is next. >> vicki:plus