I may be wrong but it looked like a long gun throwing a small fast moving round. Something like an AR etc. You'd have to be DAMN good to shoot a group that size with a pistol under serious stress and from what I've seen slow moving pistol rounds make more of a mess going thru auto glass.
One of our resident LEO's would probably have a very good guess as to what they were shooting.
I was going to say the same thing.
Also unless the gang bangers AR wasnt loaded I expect the homeowner would have to have something that looked menacing enough to scare off 4 armed thugs. If it were me I would probably just bust out the .45-70 Gov't and start slinging lead. "Don't get into a gun fight with buffalo hunters, because there ain't no such thing as cover."
An AR or an AK might be menacing enough to scare of the thugs, and it would explain the tight group.