” man who sold a high-caliber assault rifle “
That sound scary, HIGH-CALIBER!! Most likely it was a 223.
In the photo, the van windshield appears not to be penetrated, and probably was a .223 rather than larger.
About .223 Penetration
http://www.olyarms.com/index.php?option=com_content&task=view&id=14
Hey, that's bigger than a .22.