Might be a cleaning services person. Usually coworkers are unwilling to risk their jobs to steal from the office, especially if there is a security desk or cameras in the building. Cleaners, though, are typically low-wage earners who have relatively little to lose--the value of the stolen property is high enough to overcome the risk. But for someone earning, say, > $35k/year, a $1-2k camera is not worth losing that income.