(CNN) -- As a gung-ho supervisor, Stephen Jackson was so adept at finding and photographing sleeping airport security guards that colleagues called him the "Nighttime Ninja," he says.
Now the 38-year-old former U.S. Marine says he has been fired in retaliation for repeatedly bringing attention to the sleeping habits of subordinates who were supposed to be protecting New York's JFK Airport.
Jackson said he reported to his bosses about a half-dozen instances in which guards fell asleep on post during his six months at the airport.
But he says his employer -- FJC Security Services -- only took action in one case, suspending a guard who he had documented twice falling asleep.
"At JFK, they didn't want to know about it. They didn't want to deal with it," said Jackson. "I was told that, 'Listen, You fly under the radar here. You don't have to be so gung-ho.'"
Jackson this week provided the New York Post and CNN with photographs that he says show security guards asleep at JFK posts.
An official with FJC Security, which provides security for JFK, painted Jackson as a disgruntled employee who released the photos to damage the company after he was fired for misconduct.
FJC vice president and chief security officer Matt Horace said the photos were "never brought to the attention of FJC. Had he taken the proper steps as supervisor, those employees would have gone through the proper steps up to and including termination."
FJC provides security under a contract with the Port Authority of New York and New Jersey, operators of JFK.
While the Transportation Security Administration provides the high-profile job of screening passengers and baggage, airports are responsible for providing perimeter security under plans that undergo TSA scrutiny and approval.
Most large airports contract with private firms for that security work.
Jackson, of Staten Island, said he informed supervisors about sleeping guards and showed them photos. But he says he met resistance.
"My complaints fell on deaf ears, or at least somebody who didn't want to be bothered," he said.
Jackson said FJC responded differently if sleeping guards were discovered by the Port Authority or by other FJC officials. Those discovered by the Port Authority were fired, he said, while those discovered internally were not.
In May, a TSA inspector "found one of our guards sleeping" at the airport's "H post" -- an access point to an airport operations area -- and reported it to the company, Jackson said.
But the company "made no issue of it," he said.
A TSA official said the validity of that claim could not be immediately determined.
The Port Authority on Monday said it "immediately directed FJC to permanently remove from Port Authority premises the guards shown sleeping in photos and/or on video as well as any other guards caught sleeping at our facilities."
"The Port Authority will not tolerate unacceptable performance from its vendors," the statement said.
Jackson was fired May 28 for "gross misconduct and security infractions," the FJC's Horace said.
Jackson allowed an off-duty guard to photocopy log entrees.
"When we became aware of it, an investigation was pursued and Mr. Jackson was terminated."
Jackson told CNN the guard was a union shop steward and that he and another supervisor "challenged" him. But Jackson said they were told the steward had permission and that he reported it "about an hour or so after the fact."
"They suspended the other manager and fired me," Jackson said.