It was about a year ago that former NSA contractor Edward Snowden got two journalists into a Hong Kong hotel room, where he divulged some of the biggest US state secrets in modern history.

The reporters would turn the leaks into a Pulitzer Prize-winning series of reports.

But as will be explored in more depth in Tuesday night's episode of Frontline, "United States of Secrets," Snowden wasn't the first one in the US government who wanted to go public with the news that the NSA was watching everybody, including Americans.

Frontline's Michael Kirk says, in the immediate aftermath of 9/11, the NSA wanted a way to spy on American's electronic interactions. The Program, as it was called, spied on telephones, Internet connections, metadata from emails and almost every form of electronic communication. Kirk says the NSA did this without warrants, clandestinely. “To find all the needles in the haystack by finding all the needles all over the world all the time,” he says.

This is old news. But when The Program began, there were people in the NSA and others who questioned its legality, including Department of Justice attorney Thomas Tamm. His father and uncle worked at the Federal Bureau of Investigation. There’s even a photo of 8-year-old Tamm with J. Edgar Hoover. Tamm worked at the Foreign Intelligence Surveillance Court and authorized warrants. And he saw items coming across his desk of investigations and snooping that lacked probable cause. He started to wonder how the NSA was getting the information.

He asked around, but many don’t want to talk about it. His colleagues felt like something illegal was going on. “He sees this and says, ‘There is something not very kosher here, I don’t know what exactly is going on,’ and begins to worry about it,” Kirk recounts.

Tamm claims he tried to blow the whistle on the subject, working with New York Times reporter James Risen to make the story public. But Risen’s editors decided to run the story by the government. They wanted to get the governmnet’s take, before the Times revealed “The Program.” Kirk says top White House officials made three arguments to Times editors, in trying to convince them not to run the story.

1. It’s completely legal.

2. It’s a vulnerable secret. If you reveal it, hundreds of thousands of Americans may die in a future attack.

3. It’s working. You wouldn’t believe the threats we’re stopping.

Former Editor Bill Keller spiked the story, outraging Risen.

Years later, we see the impacts of the reveal. We’re continuing to debate the merits of domestic spying. Kirk says the government has yet to prove any of the three arguments it gave to Keller. And he says it causes some to question the program’s validity. But the spying program continues.

“United States of Secrets” airs May 13th, 2014 on most PBS stations at 9 p.m.