(CNN) It was just before 3 a.m. on July 31, 2013, when a federal law enforcement officer left Room 634 of the Sheraton Syracuse University Hotel, stood underneath a flagpole, put a gun to his head and pulled the trigger. The single shell casing landed near a bench next to his body.

Shortly after police arrived to investigate the shooting, so did the taxi driver who was due to take the agent to his next assignment. The dead man lying on the ground was an armed federal air marshal, a plainclothes officer whose job was to protect aircraft from terrorists. He took his life just hours before his next scheduled mission, a US Airways flight from Syracuse, New York, to Washington.

CNN has learned he is one of 10 federal air marshals who have committed suicide since 2002.

There have also been questionable accidental deaths -- such as a drowning and even a parachuting accident.

According to representatives of the Air Marshal Association , the number of federal air marshals who have killed themselves could be higher, and it is mainly due to stress.

A CNN investigation has uncovered evidence the federal air marshal sitting on your next flight may be sleep-deprived, medicated, under the influence of alcohol or worse.

And CNN has learned the Department of Homeland Security and the Transportation Security Administration may have been hiding the problem for years.

Overworked and sleep-deprived

Sonya Hightower, a recently retired federal air marshal and an officer with the newly formed Air Marshal Association, says brutal schedules -- and an even more brutal management within the Federal Air Marshal Service -- could be putting the air marshals' lives at risk and the flying public's lives in danger.

The problem, she says, stems from management that has for years placed air marshals in schedules that are physically impossible to carry out without compromising one's health.

Typical assignments include domestic missions with three to four flights a day, or quick turns on overnight international routes. Add to that the expectation that an air marshal has to be awake, alert and ready to take down a terrorist at any moment on every flight.

"Now do that 14, 15, 16 hours a day. Anybody's patience, anybody's ability to function at the highest level is going to be compromised," Hightower told CNN.

When airline schedules get delayed, so does an air marshal's sleep, which Hightower says management cares little about.

'A cry for help'

In April of 2014, sources tell CNN, a federal air marshal sitting in a cubicle in a Federal Air Marshal Service field office in West Orange, New Jersey, shot himself in the leg.

John Casaretti, a senior federal air marshal and president of the Air Marshal Association, says he believes the shooting "was a cry for help."

"I believe that the culture the agency's developed here is mind-numbing, toxic."

CNN has learned of only one incident during an actual flight. Sources say an air marshal had to be restrained by other members of the security team during a flight from Africa, where an intoxicated air marshal got into an altercation with the flight crew.

Casaretti says the New Jersey shooting, the suicides, in-flight mental breakdown and high alcohol and medication use by federal air marshals are the result of grueling schedules that include endless seemingly worthless assignments, leaving air marshals sleep-deprived and suffering in their relationships at home.

A disturbing study

In fact, the government has evidence that armed air marshals are so dangerously sleep-deprived that it could affect their ability to thwart a terrorist attack.

In 2012, the TSA was given results of a commissioned sleep study on air marshals. The results of the study -- now classified as sensitive security information -- were disturbing.

Seventy-five percent of air marshals flying domestic missions were sleep-deficient.

On international runs, the figure rose to more than 84%.

In a job where it is critical to be alert and accurate at a moment's notice, the study finds "the acute and chronic lack of sleep substantially degrades a Federal Air Marshal's ability to react and think quickly."

The study, conducted by the Division of Sleep Medicine of Brigham and Women's Hospital at Harvard Medical School, found half of federal air marshals take some medication or supplement to get to sleep. Others commented they turn to alcohol.

Asked in a survey if they consumed as much as five to six beverages a week, one air marshal responded, "Give us a break Harvard!! 8-12 per night on an overnighter, and the same just to sleep at home."

Other air marshals echoed that response.

"Most of the sleep patterns that I have are broken."

"This is not healthy."

"I need to take sleep aids."

"alcoholic drinks ... mixed with sleeping pills."

The study, obtained by CNN, says federal air marshals suffering from fatigue have increased risk of "self injury ... fatigue-related motor vehicle accidents, and greater incidence of serious errors."

'They chew us up and spit us out'

"The agency was put on notice with the sleep study that air marshals will make mistakes," said Casaretti, noting that the study recommends an equal amount of recovery time vs. travel time.

"That would never happen," he said. "So, they chew us up and spit us out year after year after year."

Sonya Hightower took part in the study, and she says for the last three years, the Department of Homeland Security has been trying to hide the results.

"Air marshals are exhausted," she said. "They are having memory loss, they are being forgetful. At some point, they are working long enough hours that they are legally intoxicated. ... They can't move. They can't respond fast to things. And the agency was not prepared for someone to document that as well as Harvard did in their study."

The study was sent to the entire Federal Air Marshal Service workforce, but was then classified as sensitive and prohibited from being distributed.

Hightower says her real fear is that no one inside the DHS, the TSA and especially the FAMS is willing to admit that thousands of armed air marshals, flying on plane after plane, are providing little added protection and could be posing a threat to themselves or the flying public.

That's why she is now going public with her concerns, fearing it will take a catastrophe to get the administration's attention.

"I hope to God we don't have to go through that. I don't want that to happen ... and it worries me," Hightower said. "Nobody is listening."

FAMS: 'Robust' assistance available

The Federal Air Marshal Service turned down CNN's request for an interview, and instead issued a statement from Director Roderick Allison.

"The health and welfare of every man and woman who serves in the Federal Air Marshal Service (FAMS) is TSA's highest priority. TSA is committed to providing them with the resources and support they need to carry out their mission, and any loss of life is unacceptable."

"As part of our efforts, FAMS maintains a robust system of both medical, including mandatory physicals, and psychological assistance programs which are readily available to the workforce and their families. The FAMS Medical Programs Section is staffed with a physician and other full time medical professionals who are available to FAMS personnel 24/7 and upon request."

A TSA official insisted that air marshal schedules ensure appropriate rest periods and told CNN that in response to the study showing an overwhelming number of sleep-deprived air marshals, "recommendations were adopted to address FAM schedules to include, the creation of an educational training DVD which was made available for viewing in each (Office of Law Enforcement)/FAMS field office during quarterly training. Questions related to sleep and fatigue are asked during the FAMs mandatory physical exam and responses are reviewed by OLE/FAMS Medical Programs Section. Finally, if an OLE/FAM employee suspects he or she has a sleep disorder, consulting his or her primary physician is recommended. Additionally, FAMs have access to a robust Health, Fitness, and Wellness Program."

Senate Homeland Security investigation

The U.S. Senate Homeland Security Committee, headed by Sen. Ron Johnson, R-Wisconsin, has begun looking into the high rate of suicides among federal air marshals as part of a wide-ranging probe of the management of the estimated 3,500 U.S. air marshals currently assigned to U.S. air carriers on domestic and international flights.

According to Johnson, "The Homeland Security and Governmental Affairs Committee is continuing its bipartisan investigation into the Federal Air Marshal Service. The committee is examining allegations of misconduct, mismanagement and waste and is continuing discussions with agency officials and employees regarding the service."

The U.S. Federal Air Marshal Service ballooned after the attacks of September 11, 2001. The agency grew from several dozen air marshals to several thousand. The secretive agency has been thinning its ranks in recent years and trimming its budget.

An email obtained in February 2014 by CNN from then-Director Robert Bray put the agency's budget at $805 million. Last year, the agency announced the closing of six of its 26 field offices by June of 2016.

According to Casaretti, armed air marshals have been relegated to simply flying on plane after plane, with few results, no ability to conduct investigations, and few opportunities to advance in their careers.

"There's a need for what we do. We should be primarily an anti-terrorism group that does a finite job of detecting terrorists and working with anti-terrorism," Casaretti told CNN.

"I see no value in an air marshal simply sitting in a seat and bouncing back and forth from coast to coast for no other reason than he has to do something."