When Delko tells Natalia about Clavo Cruz, Delko says Cruz was put way for deliberately running over a model with his car in season 2. Cruz was never formally charged or arrested for that crime, but for the murder of another woman in Season 3.
A boy is supposedly shot accidentally by his brother using one of the confiscated guns. Confiscated guns slated for disposal should have been unloaded and otherwise rendered unusable, e.g. firing pin removed.
During the teaser, a van is propelled up from the road by way of an explosion. However, the van is pushed up a frame or two before the explosion (and resulting smoke etc) occurs.