The resignation of the top official in the Environmental Protection Agency's South and Southwest region—the heart of oil and gas country—is providing further ammunition to GOP lawmakers who have been vocal critics of the agency.

Al Armendariz, EPA's Region 6 administrator, resigned after a two-year-old video in which he used the word "crucify" to describe his enforcement approach to firms that break environmental laws became public and caused a national stir.

Armendariz, appointed by President Obama in 2009, sent a letter to EPA Administrator Lisa Jackson on April 29 apologizing for the remarks. Jackson accepted his resignation on April 30.

In the 2010 video, Armendariz said that, like Roman conquerors who "crucified" local townspeople to make examples of them, he sought to make examples of oil and gas companies that broke environmental laws.

In his letter to Jackson, Armendariz said he regretted making the comments and that they were not representative of his work as administrator of EPA's region that covers Texas, New Mexico, Oklahoma, Arkansas and Louisiana.

Armendariz was considered something of a lightning rod in Texas. Environmental groups strongly supported him, crediting him with being tough on polluters. During his tenure, the EPA overturned a number of "flexible" air permits issued by the Texas Dept. of Environmental Quality to refineries and other industrial facilities during the George W. Bush administration.

Under the flexible permits, facilities agreed to reduce overall emissions of pollutants but not every pollutant under the Clean Air Act, says Ken Kramer, director of the Sierra Club's Lone Star Chapter.

But conservative lawmakers think Armendariz reflects what they believe is an overzealous EPA. Sen. James Inhofe (Okla.), the ranking Republican on the Environment and Public Works Committee, assailed Armendariz in a floor speech on April 25, highlighting the comments made in the video.

Shortly thereafter, the White House and Jackson publicly distanced themselves from Armendariz. At a public meeting, Jackson called Armendariz's remarks "disappointing." With only "lukewarm support" coming from Jackson and the administration, "the writing seemed to be on the wall for him in this contested election year," says Frank Maisano, an energy analyst with the Washington, D.C., offices of law firm Bracewell & Giuliani.

Inhofe says Armendariz's resignation "in no way solves the problem." He says there were at least three cases in which the EPA suggested that hydraulic-fracturing activity had led to possible groundwater contamination in Texas, but then the agency backed off those allegations when it could not find sufficient evidence. "The American people deserve to know why … EPA tarnished the reputations of companies" with no definitive evidence to prove the link between fracking and groundwater contamination, Inhofe says.

But Kramer says that Armendariz, a former college professor and environmental engineer, "really comes from a scientific background. … He is not a person who based his decisions on questionable science."