Bypass Congress, bypass the DOJ, bypass the current administration in Washington entirely. It's time the State's Attorney Generals of Arizona and Texas got into the act and ordered an investigation based on the deaths of Agents Zapata and Terry. The persons who purchased the weapon that killed Agent Zapata are already being held in a Texas jail. Let these criminals testify and put the heat on the ATF from another direction; a direction they can't bury or cover up.
Negligent homicide is still a felony under both Arizona and Texas state law.