Sparteye has the right of it ... police persons{chuckle} tend to talk about 'individual(s") because it is part of police jargon and includes both male and female.
Person or persons is used so as not to give any indication whether or not the police are looking for one person or a bunch.
The cops are just trying not to give anything away to the bad guys/gals.
When I was covering police beat (1960s & '70s) the term perpetrators was common in CopTalk - because it was gender neutral and looked important in reports -- when writing up police stories I used person. I did not want people to forget that whatever actions were being taken a person was involved. Too easy to objectify a human being by using perpetrator. About the time of TV's "Hill Street Blues" was first time I heard "perp" -- as a pejorative to indicate contempt. The derisive meaning seems to have become most accepted now-a-days.
