Image copyright Celia Randolph Image caption Celia's husband Jason, an IT consultant, and their son Christian in 2006

It's a story that sounds impossible. Lightning never strikes twice, so they say. Except when it does."I want our story to remain shocking forever - but I'm worried that already we're not alone," Celia Randolph says.

On the surface they are a normal family - mum, dad, four kids. They've lived in small towns in America that seemed safe.

Celia's children speak carefully and precisely, like their mother. "I'm not an emotional person," Celia explains. "But I'm now very angry and I'm very sad. America has failed our kids. What happened to my daughter in 2006 shook me and my husband to the core."

Then on Valentine's Day this year she got a text. Celia saw the words: "You're not near Parkland are you? There's been a shooting."

"I kept saying to myself, 'Not again, not again'." Celia dropped everything: "When it happens, you run. You run." Her son Christian is a junior at Marjory Stoneman Douglas High School, Parkland, Florida.

Image copyright Celia Randolph Image caption Celia Randolph, 58, lives with her family in Parkland, Florida where she is a lawyer

The first time someone called Celia to say a gunman was in her child's school was 12 years ago.

She and her husband Jason were 50 miles from home. "We raced to get to her."

Chelsea was 14 years old and they were living in Bailey, a small mountain town in Colorado. The Columbine massacre, in which 13 people were killed, had happened in 1999 just under an hour away but the beautiful forest and mountains gave their home a secluded, quiet feeling.

When Chelsea tells her story - which she's never spoken about publicly before - she's anxious: "What happened to other families is worse. Don't overshadow them."

She's talking about the family of her friend Emily Keyes - the 16-year-old was killed in the violent end to a hostage crisis in their school in 2006. The gunman had entered the Platte Canyon High School with a handgun and a rucksack he said held explosives. He took six girls hostage in a classroom. The siege ended four hours later when a Swat team blew a hole in the wall.

At first Chelsea hid under a table in the classroom opposite, holding her best friend's hand. When a Swat team knocked down the door, they escaped.

"You have to understand, to see a man with a full-on vest, with full-on attire, and a gun bursting into your classroom telling you to get out - you have no idea what is going to happen to you," she says. "As we ran out, in every corner we saw a Swat man with a gun. I saw my friend in one classroom, petrified and pale. He couldn't speak."

Once Chelsea made it home with her parents, they watched the crisis play out on TV. She watched helicopters, police, guns swarm over her school. "We didn't know who the hostages were but we could piece together the classroom timetable and who would have been in there."

Accurate information was hard to come by. Her only option was to watch TV to find out what happened to her captive classmates. "We saw the girls released one by one - there was a hill by the school and we watched them running for their lives up it."

After a pause, she continues, "I remember an image of a stretcher coming out of the school and put in a helicopter."

Image copyright Celia Randolph Image caption Chelsea Paz at her 15th birthday party, months after she witnessed a school shooting

The shootings shattered Celia: "it was very, very difficult. You just think, 'I can't protect my kids.' It's horrible.

"It took away the sense of security that I hoped my children would have. A stranger came into our world and did this terrible thing. You felt like, if it could happen there, where could you keep your family safe?

"We raised our children teaching them to be more afraid of harm from animals than from people."

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She consoled herself with the thought that she didn't feel it was a targeted attack on the school. "The emphasis was on healing and performing random acts of kindness. We all considered it a random act of violence rather than a 'school shooting'."

But her sadness made her feel guilty. "I would think I get to hug Chelsea, what's wrong with me for being upset?" She says looking after a traumatised child took its toll, but that she and her husband gave their children a stable upbringing. "We have good family relationships and we loved them. I don't think it changed our family life permanently."

Chelsea finished the school year and in 2007 the family left Colorado, returning to Celia and Jason's roots in Florida.

Family life ticked by and although Celia never felt that she had closure, she says they've been "very blessed". Twelve years on, gun laws have barely altered in the US. An estimated 57 mass shootings have happened between 2006 and 2018. Still, Celia found it unimaginable that it would happen to another of her children.

Image copyright Celia Randolph Image caption Christian Paz, 16, studies at the high school in Parkland, Florida, where a gunman killed 17 people on Valentine's Day

The second time someone called Celia to say a gunman was in her child's school was two weeks ago.

Christian is 16 and is quiet with a calm manner. He's smart and Celia and Jason chose Marjory Stoneman Douglas, in Parkland, Florida, for its academic reputation.

He was in a culinary class when he and his classmates heard shots. Their teacher, Ashley Kurth, pushed them into a cupboard. "At first we didn't take it seriously but then we got quieter and quieter. I resigned myself to the floor. I couldn't convey any emotions because we had to stay silent. People were texting their parents, but I couldn't - I had forgotten to charge my phone."

After getting the news, Celia ran to her car. She got as close to the school as possible. "I couldn't get any information. I was texting him and he didn't respond," she explains. "That killed me. I was only thinking, "Is my child alive? Is he scared? Is he injured?"

A barricade was blocking parents' access to the grounds as police searched for the gunman.

Christian's teacher let into her classroom more children who'd been trapped in hallway. They listened to police updates through a walkie-talkie. She reassured the teenagers that, should the gunman find them, they were in a kitchen surrounded by huge knives.

Like his sister, Christian remembers the Swat team bursting in: "They shouted, 'Hands up, lie down.' They couldn't be sure one of us wasn't the shooter."

On the way out Christian saw blood on the stairs outside his classroom. "We ran to the street. There were helicopters, police, military equipment everywhere. We were allowed to see our parents. At first I was so happy I was out of there but then I became sadder and sadder."

While Chelsea had felt isolated by the memories of what she witnessed, Christian has the dubious fortune of having a sibling who also survived a shooting.

Image copyright Celia Paz Image caption Following the shooting in Colorado Christian's sister Chelsea went to college and got a job in IT

"She told me she too wanted to stay inside when it happened, that it took her a while to feel anything, that she felt numb at first. She said she broke down, got better, then four years later broke down again. For all the wrong reasons, it's wonderful to have her. She already knows what's going to happen to me - she's just waiting," he says.

For Celia, two weeks after the Parkland shooting, the realisation that not one but two of her children have been caught up in and, thankfully, survived school shootings is sinking in.

Celia's experience means she knows what's coming for the Parkland community, even before they do.

"The other parents and children injured will be dealing with their trauma for a long, long time. I feel sad I know what's going to happen next."

"I'm really struggling to cope with the idea that two of my children had to dodge bullets. It's so sad to me that I have a child that went through it and now has to comfort her little brother."

She's in a community message group - members recently asked what the millions of crowdfunded dollars will be used for. After all, the funeral and medical expenses of the victims will be met by the local county.

"There are costs they can't imagine right now. The parents who can't work because of hospital visits or caring for traumatised kids still have mortgages to pay. It's for the counselling for the kids, which will take years. But they don't know all of that yet," she explains.

She's seen one community cope with the aftermath of a shooting already. Although she says Bailey "came together in an amazing way" she says "processing what's happened takes time".

Image copyright Chelsea Paz Image caption Chelsea and Christian at their elder sister's wedding last year

"Not all the kids in Parkland are going to do well. They're not all going to come out of this OK. You don't have a concept of how long this road is going to be, and not only for the victims' families," she warns.

It's the first time she's told many people what happened in 2006 - the reaction is one of shock. The family, who found the media circus in both shootings intrusive and traumatising, want to speak publicly to call for an end to school shootings. "We are not anti-gun, but we are against these weapons of war being so readily available. We need not to fail our kids. People can't believe our family has been through two shootings, but I'm not so sure the chances aren't pretty good of there being more like us unless we do something about this."

The teenagers from Stoneman Douglas went back to school last week, some of them now famous for their passionate calls to end to gun violence. In the days since the shooting, President Trump shocked lawmakers by calling for the type of gun law changes that Republicans rarely back, and major retailers have reduced access to some weapons or ended links with the National Rifle Association.

Celia has seen the cycle of violence, public outrage and a return to status quo many times. "If Sandy Hook couldn't change things, will this?"

She wants the conversation to move away from debates about mental health and expanding access to guns to teachers, saying: "Until there's alternative political funding that's not from the NRA, there won't be any change."

But she believes there is something different this time. "These kids have access to social media and are very articulate but also privileged. The kids have shamed the adults into action. I love them dearly for it and my family has joined them. Now they need to go to school and just be kids. It is our duty as the adults. It's not too late for us."

On Wednesday, Christian returned for one day to the classroom where he hid from a gunman. "I do know that he has not yet been hit with that punch of realisation of what he and his school have been through. This is where my experience of the past makes me sad. That said, it makes Jason and I more understanding of him when that time comes," Celia explains. The next day, events began to catch up with Christian and he was unable to go to school.