They were out to investigate a complaint. When there was no response to knocking at the door, they asked dispatch to telephone the "RP" (reporting party) and have them come to the door. That they all subsequently backed away out of the porch light and waited in the dark with guns drawn doesn't make much sense to me.
If you're not getting an answer when someone has called you out, the first thing you do is double-check that you have the right address and that that address matches the one you're standing at.
If I see blinding light pointed at my door . . . it ain’t no B&E or mugger . . . it be PO PO . . . LEAVE THE GUN OUT OF SIGHT !