A Louisiana man helped file a lawsuit on Tuesday that accuses a sheriff's office of withdrawing a job offer after finding out that he has HIV.

William Pierce told ABC News that he was hired as an Iberia Parish sheriff's deputy in 2012, but lost the offer after his medical examination exposed him as HIV-positive.

"It was a punch in the gut," he said. "It was a done deal until they found out I was HIV-positive. That was devastating."

Lambda Legal, which takes on civil rights cases for LGBT and HIV-positive people, filed a lawsuit on behalf of Pierce against Sheriff Louis Ackal and Capts. Ryan Turner and Rickey J. Boudreaux in federal court in Lafayette.

The lawsuit explained that Pierce, who is healthy, takes his medication and is regularly checked out by his doctor, did not pose a significant risk to anyone he encounters as a police officer just because he has the virus. It also argued that rescinding the job offer was a violation of the Americans with Disabilities Act.

Pierce says he took the case to the Equal Employment Opportunities Commission, which then spent several years on it. In February 2016 he was told that the sheriff's office likely violated the law, and was then told he had a right to sue.

He decided to remain in Louisiana because he loves the people, but says the state is falling behind on HIV education, adding that "that's one of the reasons Louisiana has a high infection rate—because of the lack of understanding."

It's that lack of education that Pierce says cost him the job in the first place.

"It's the equivalent of not hiring somebody because they had cancer or diabetes," he told ABC News. "It's not the 1980s any more. We don't have to be afraid."