Twenty eighy unarmed migrants have died at the hands of U.S. Customs and Border Protection since 2010–and not one agent has faced criminal charges in the killings. Two months ago, the Border Patrol’s head of internal affairs, James F. Tomsheck, was fired for not doing enough to investigate the shootings. But since that time, Tomsheck’s gone on the record to refute that claim, and to tell the public just corrupt the agency has become.

Tomsheck spoke with NPR in a report that aired this morning. He explains that agents routinely lie or distort the truth to protect themselves. But the problem isn’t individual agents–it’s the leadership, too. And, according to Tomsheck, the agency itself tends to think of itself as a “paramilitary border security force” that’s operating outside of the “constitutional restraints regarding use of force.”

The Border Patrol is largest federal law enforcement agency in the United States. It says it is launching a new training program, as well as an improved internal affairs unit headed by the F.B.I.