Shanti Viswanathan, a US teacher of Indian origin, saved the lives of her students during the school shooting in Parkland, Florida, on 14 February. In her first media interview, an exclusive, she spoke to BBC Tamil's Aarthi Gnanasekaran about how that day unfolded.
It was around 2.15pm. Ms Viswanathan was half-way through her fourth period algebra class at the Marjory Stoneman Douglas High School when they heard gunshots.
"As soon as I heard the shots fired, I said drop everything, leave everything," Ms Viswanathan said.
She said students who were working on their laptops asked if they should put them away. "I said leave the laptops," she recalled. She told them to crouch or hide in corners so they wouldn't be visible from the small glass window in the centre of the classroom door.
"I might have said it was a drill because I wanted to reassure them. I didn't want anybody panicking," she added.
While some of them scrambled to hide under her desk, she locked the classroom door, covered the window with a sheet of paper and turned off the lights. And then they waited.
According to police reports, 19-year-old Nicholas Cruz arrived on school premises at 2.17pm in an Uber car. He entered the school wearing a gas mask and carrying a rifle, ammunition cartridges and smoke grenades. He then set off the fire alarm so students and teachers would leave the classrooms and pour into the corridors.
The first shots were at heard at 2.21pm when he fired into classrooms on the first floor. In the six-and-half minutes that followed, he shot dead 17 people - 15 students and two teachers.
Ms Viswanathan's classroom was on the second floor. "It was all quiet. I told them to stay silent," she said - she hoped the gunman would assume the classroom was empty.
She said she saw the door handle move - perhaps he tried opening the door. But he moved on.
She said it was purely "presence of mind" because she had never been trained for a scenario such as this.
No-one would have expected this, she added, because Parkland - a leafy city just an hour from Miami - had recently been declared one of the safest cities in the region.
Even when the police turned up to evacuate the classroom, Ms Viswanathan said she refused to unlock the door. Instead she asked them to get the key from school officials or break down the door - and they eventually did.
"It was like a war zone… blood on the stairs, in the hallways, blood in front of the building, bodies being dragged," she said. "I know a teacher who had to cross eight dead bodies before she was evacuated.
"Is this really the safe haven we had created for students to learn? Is this a place of learning or is this a place of death?"
Mr Cruz, a former student who had been recently expelled, was arrested at 3.41pm, a few miles from the school. He had left his weapons in a stairwell in the school building and then blended into the crowd of students as they exited with help from the police.
This was the sixth school shooting of 2018 in the US. And it was the worst since 2012, when gunman Adam Lanza attacked Sandy Hook Elementary School in Newtown, Connecticut. He shot dead 20 young children and six adults before killing himself.
But the attack in Parkland ignited a youth-led anti-gun movement that has swept the US.
Within days, the #NeverAgain movement gathered support on social media and sparked countrywide protests for tighter gun control, with the students from Marjorie Stoneman Douglas High School becoming its fiercest advocates.
"I am so proud of our... children," said Ms Viswanathan. "All these kids have been our spokespeople, they have done such a wonderful job representing this whole movement."
What does she think of US President Donald Trump's proposal that arming teachers could prevent school shootings?
"A good guy with a gun can catch innocents in the crossfire, a good guy with a gun can still not stop a guy with an AR-15," she said.
Ms Viswanathan would not say what age of the students in her class were but she did say her relationship with them has changed.
"Right now, they have a new-found respect for me because we have been through something together."
But, she added, more than two months later, they are still anxious. "They keep looking at the door, they keep looking at the window, they are afraid to go the bathroom."
"There is no reason for a civilian to hold an assault rifle no matter what. This should be the last mass shooting to ever happen, we should not have any more mass shootings. Ever."