Roy,
Unfortunately I have followed too many cases to fall for the line "person or persons". Our PC world has forced LE to also become PC. One thing about it though, in the cases I have followed where ther are persons - two weeks tops before there is an arrest because one always gets the snot scared out of them and rolls on the other. i.e Bobby Cutts & Myeisha, Speers & Collings and so it goes.
Cop speak in my opinion.
That is what I am saying. I thought you were placing emphasis earlier that the Chief was confident in solving this crime. That statement is cop speak as well.