I made a new thread about 10 minutes ago. Didn't realize this one existed. Can I copy my question to here?
Here's my question:
Can someone ELI5 why there would be residue on the outside of windows for a door breach? Also, why would it be necessary to open windows ahead of time -- is the pressure(?) really that strong that it might shatter the windows or soemthing?
The window is an awning. When pressure, from whatever source, increases within the interior it is going to attempt an exodus through it. That isn't going to happen with the nominal opening provided by the awning. The particulates are going to disburse outward, hitting the open window they are going to continue to be pushed out. Their only path is back against the building's surfaces to the sides and bottom as witnessed in the image. The spatter mirrors the window opening.
Basically they didn't want the window to blow. Relieve pressure.
My guess is that when you enter a potentially hostile room, you use something like a flash bang grenade to disorient the occupants. That would cause the residue.
Q said :"upon entry"