WASHINGTON -- With "Making a Killing: Guns, Greed, and the NRA," documentary filmmaker Robert Greenwald wanted to dig deep into our national gun debate and chronicle the horrifying consequences that have come with easy access to firearms. The film is divided into segments ranging from the intimate (domestic violence ) to the very public (mass shootings). In one section, Greenwald looks at the link between guns and suicide .

According to the Means Matter project at Harvard's School of Public Health, more people who die by suicide use a gun than all other methods combined. It's become enough of a problem that concerned gun shop owners are starting to address the issue in states like New Hampshire, Maryland and elsewhere.

In the documentary, Greenwald tells the story of Kerry Lewiecki , a bright young man about to get married, and his suicide by firearm -- a tragedy that shocked all who loved him. Greenwald relies on interviews with Lewieckis parents and his fiance, Sara Miller, allowing their tragic story to illustrate what's really at stake in the debate over waiting periods for gun purchases.

In an email exchange with The Huffington Post, Greenwald said that he'd hesitated to include a section on suicide in his film. He said his misconceptions about suicide made him think it wasnt worth exploring. In his words, he'd "bought into the myth that anyone who wants to commit suicide will do so." But he soon learned that it's not always so black and white. There is something politicians can do to help prevent some suicides from happening.

This interview has been edited for length and clarity.

How did you find this story and why did you want to tell it?

Our team of researchers found a piece that Sara and Kerrys father wrote for a scientific journal about suicide/guns as a public health issue. [Their story had also been covered in The New York Times in 2013.]

I met Sara for tea and as she told me the story about her and Kerry, the power of the love story grabbed me by the throat. I was deeply moved and never wavered from that moment on in my commitment to telling that story.

What was it about Kerry's story that made you want to feature it in your documentary?

The love story. The fact that anyone could relate to it. The universality of the story. And the potential to use it to touch people's hearts to go to their brains and then to action.

The stunning detail -- the receipt that showed that Kerry may have purchased the gun within an hour or so of killing himself -- really stands out. Was there an attempt to talk to the gun shop owner?

No.

Why not contact the gun shop owner or gun shop owners to get their side of this debate?

It is not about the gun shop owner, it is about the laws and policy he/she is working under.

Why do you think waiting periods are viewed as controversial?

I dont think they are controversial. I think it is a function of gun companies/the NRA creating irrational fear among a small subset of people.

Had Kerry had any interaction with the mental health system prior to his suicide?

No. None.

Kerry's gun purchase seemed to surprise his loved ones. Had he any experience with firearms?

No experience of any kind, ever.

Where did Kerry purchase the gun? What are the laws in that state around waiting periods?

Kerry purchased the gun in Eugene, OR. There are no waiting period laws for firearms in Oregon.

What do you hope telling this story accomplishes? What do you want viewers to understand about suicides by gun?

I originally did not want to do a gun suicide story. I believed that if someone wants to commit suicide they will. So why do the story? Boy, was I wrong. So I wanted to tell the story to help others feel and understand that suicide is a momentary impulse. That many of us go to dark places, sometimes for long periods, sometimes for short periods. But the darkness passes.

With a gun instantly and easily available there is no time for the pain and despair to pass.

If there were time (a waiting period) many lives would be saved.

Why do you think you had this misconception about suicide?

I had bought into the myth that anyone who wants to commit suicide will do so. I had not thought through or seen the research about suicide being an impulse, and that when the impulse passes, and the despair leaves, the impulse is gone.

Why did you decide to release the film this way, with free screenings?

Our goal with this film, and all the other Brave New Films, is to create social change rather than profit. To do that we need the largest possible audience... We need people to take action. We need to provide a tool that anyone can use to reach out to their friends, relatives, schoolmates. That is not possible if we charge.

For information about screenings of "Making a Killing" near you, go here .

If you or someone you know needs help, please call 1-800-273-8255 for the National Suicide Prevention Lifeline . Outside of the U.S., please visit the International Association for Suicide Prevention for a database of international resources.