On March 16, 1968, U.S. Army Soldiers opened fire on an entire village of unarmed civilians in South Vietnam, killing hundreds of women and children.
It became known as the My Lai Massacre, and it has been marked in the history books as one the most atrocious acts of the Vietnam War.
The New Yorker's Seymour Hersh, who broke the story as a 32-year old freelance reporter, remembers how he first found out about it.
"In 1969, I got a tip from an anti-war person that there had been a horrible massacre. I put aside whatever else I was doing because I just frankly thought that made sense."
Hersh went on to win a Pulitzer Prize in 1970 for his exposé. He recently traveled to My Lai for the first time to get a sense of how the region, and the country, are faring nearly 50 years later.
"It was traumatic because it was as I had envisioned it. I knew a lot about what happened. I knew places. There was a ditch I knew very well," said Hersh.