Hours after a New York Police Department officer died by suicide, Frank Dowling, a psychiatrist who works with members of the NYPD, tweeted a plea to those in uniform.

"NYPD officers — look in the mirror — take a good look at your coworker ... ask your partner are you OK?" he posted Thursday.

The latest suicide of a member of the NYPD — the fourth in three weeks — has rattled the nation's largest police department and led its top brass to once again highlight available resources. Mental health professionals and policing experts also say it's time for the entire profession to redouble outreach efforts and reevaluate its strategy for how to destigmatize depression and mental illness within the high-stress job.

NYPD Commissioner James O'Neill told reporters on Friday that the department will review how it tackles mental health and suicide prevention, including offering peer-to-peer counseling at every police station.

"It's not an ordinary job. People face a lot of stresses they're exposed to, a lot of trauma," O'Neill said.

Cops have extremely difficult jobs & we need to make sure we’re doing our best to protect every member of the NYPD. We’re looking at all the ways we can get support & treatment to our people, including peer-to-peer counseling in every station house. ➡️ https://t.co/kmAsl0HHQI pic.twitter.com/lw57lD29Bg — Commissioner O'Neill (@NYPDONeill) June 28, 2019

Dowling is also a medical adviser to the nonprofit Police Organization Providing Peer Assistance, or POPPA, which offers mental health support to NYPD officers and was formed in 1996 after 26 members of the department killed themselves during a two-year period.

This latest string of deaths in such a short time is the worst Dowling can recall since.

"If this continues, oh my God — but hopefully this cluster settles," he said Friday.

Data on suicide rates in law enforcement has been historically incomplete, but recent studies show more officers die by suicide — at least 167 officers in 2018 — than are killed in the line of duty, according to Blue H.E.L.P., a nonprofit made up of active and retired police officers.

The Ruderman Family Foundation, a private philanthropic organization, found last year that post-traumatic stress disorder and depression rates among police officers and firefighters are as much as five times higher than for civilians.

New York City has averaged about four to five police officer suicides a year since 2014, officials said, and in the past six months, there have been six.

After the third suicide of an NYPD officer this month, O'Neill declared a "mental-health crisis."

"There is no shame in seeking assistance from the many resources available, both inside and outside the department," O'Neill said in a June 14 statement. "Accepting help is never a sign of weakness — in fact, it's a sign of great strength."

His comments followed the fourth NYPD officer death on Wednesday, which NBC New York reported involved a 24-year department veteran who served in the Bronx and shot himself while off-duty at his home on Long Island.

The other incidents this month involved a deputy chief who was set to retire and a veteran homicide detective — both of whom died within 24 hours of each other — and a 29-year-old patrolman who took his life outside of a precinct on Staten Island.

The city of Chicago has also grappled with a cluster of police suicides, with at least three this year and four last year, officials said.

O'Neill said his department reached out to Chicago's police superintendent, Eddie Johnson, who recommended New York look at expanding its peer-to-peer resources and evaluate its policy for when an officer's firearm should be taken away.

"One of the biggest challenges — and why it takes courage to get help — is as someone's becoming anxious, depressed, jumpy, maybe starting to self-medicate with alcohol, get burnt out, it becomes tougher for that person to believe they can get help and that help will work," Dowling said.

In April, the NYPD and the Police Executive Research Forum, an organization that works to improve the professionalism of policing, hosted a symposium on law enforcement suicide. The forum's executive director, Chuck Wexler, said an important takeaway was that police departments and other law enforcement agencies must do a better job of capturing and analyzing police suicide data because "the research is really uneven."

"We advocated that agencies should conduct psychological autopsies on suicides and learn what were the circumstances that resulted in these tragedies," Wexler said Friday.

"We don't even know how many people have attempted suicide," he added.

The danger is amplified for officers who are battling depression and mental health issues because they have easier access to weapons, Wexler said. For some officers, he added, the idea of coming forward about their mental health — then having their firearms confiscated for safety — can only make them less likely to speak up.

"There's no question that what makes police officers at-risk is because they have an occupational need to have a firearm, and in many of these cases, firearms are the way officers take their lives," Wexler said. "You've got a combustible mixture when you have someone who's dealing with some significant personal issues and the availability of a firearm."

Sean Powers, a 12-year veteran of the NYPD who retired in 2005, said the fear for some officers is not only that their guns could be taken away, but they would be placed on desk assignment or left monitoring surveillance cameras instead of being out on the beat.

"You lose your identity," he said.

Powers, 56, became a volunteer with POPPA, the peer-assistance program, with the desire to help his fellow officers, many struggling with trauma from 9/11. Not long after joining POPPA, he said, he got a call from an officer who was threatening to shoot himself in a quiet parking lot outside of a church on Staten Island. In that case, the officer was helped before he could do any physical harm.

While the NYPD and the city of New York provides internal resources to officers, POPPA offers anonymous counseling services outside of the department. And having a fellow officer to turn to can be advantageous over someone unfamiliar with law enforcement policies, Powers said.

"Sometimes we get cops who really need to vent, and so you understand the lingo and the jargon. You might not have worked at the same exact precinct or done the same exact job, but you know what they're talking about," he added.

Powers, who also has a sister in the NYPD who volunteers with POPPA, knows he has made a difference when he gets Christmas cards from officers thanking him because they decided not to take their own lives and instead spent another holiday with their families.

After the recent spate of suicides within the NYPD, Powers said, he has reached out to people he knows on the force and asked them to look out for one another.

"It's frustrating seeing this happen in your own backyard," he added, "and you think, 'Why didn't he call?'"

Editor's note: If you are looking for help, please call the National Suicide Prevention hotline at 1-800-273-8255. You can also text the Crisis Text Line for help by messaging 741741 with the word HOME; police officers should text the word BLUE.