megyn: new developments now on the gun running sting tpwopb wrong for the department of justice. we showed exclusive video of the dea rounding up drug cartels on u.s. soil. guess what else they found? guns. the same guns the feds were supposed to be tracking as they were purchased in arizona and then shipped right into the hands of mexican drug lords. william la jeunesse is live in los angeles. william. reporter: critics often called the border a revolving door. today stunning evidence of why and what happens when government agents knowingly allow guns to walk or not stop them. last week we joined police for a billion dollar bust of the sinaloa cartel. cops arrested 76 associates and seized $800,000 in cash. on monday police held a news conference announcing their accomplishment. but get this. five hours later they arrested this man, driving 50 miles an hour in a school zone with