When her son was four, American author Gin Phillips spent an inordinate amount of time with him at the zoo.
While observing the giraffes at their local zoo in Birmingham, Alabama, for what seemed like the 4,000th time, she began to wonder what she would do if her worst nightmare came to pass there - gunmen breaking in and threatening the life of her son.
In her new psychological thriller Fierce Kingdom, a woman and her young son have to survive a mass shooting at the zoo by men who think nothing of gunning down animals and humans alike.
Phillips, 42, says over the telephone from London, where she is on a book tour: "I wanted to set a whole novel around motherhood, looking at the relationship between mother and son in the most intense situation possible."
Her son is now six and she also has two stepchildren aged 19 and 15.
Fierce Kingdom is her fifth novel and unlike anything she has written before. Her previous work has often looked back through time - her 2009 debut The Well And The Mine was about coal miners in 1930s Alabama, while in Come In And Cover Me (2012), an archaeologist is able to see the ghost of a 12th-century potter at a New Mexico dig site.
In contrast, Fierce Kingdom unfolds in the space of three hours, as desperate mother Joan and her four-year-old son Lincoln hide in the zoo, trying to escape the shooter.
Split-second decisions could save or endanger their lives. Should Joan keep her phone on so she can stay in touch with her husband outside, or will the light from the screen draw the gunman's attention? Should she leave cover to get food for her hungry child or let him starve and risk him throwing a tantrum?
But the worst decisions she has to make involve the children of others. Throughout the night, she repeatedly encounters other people and must decide if she should help them and risk Lincoln's exposure or abandon them to their fates.
"There is the idea, on the one hand, that motherhood is incredibly selfless, that your needs don't matter as much as this other person's needs," says Phillips.
"Yet, on the other hand, it is also selfish - I take care of my child and if anything happened to him, my life would be shattered. What do you owe to your own child and what do you owe someone else's?"
Movie rights for the book were picked up at the end of last year by Australian actress Margot Robbie, who will co-produce the film for Warner Bros through her LuckyChap Entertainment production company.
Phillips is excited, but also feels some trepidation. "It would be hard to see a story I feel personally about turn into something I don't recognise."
With the spate of gun violence in the United States, the fear of being caught in a shooting is "in the back of many people's minds", she says.
There is the idea, on the one hand, that motherhood is incredibly selfless... Yet, on the other hand, it is also selfish - I take care of my child and if anything happened to him, my life would be shattered. What do you owe to your own child and what do you owe someone else's?
AUTHOR GIN PHILLIPS, whose novel explores how a mother tries to keep her young son safe
Slightly more than a year ago on June 12 was the worst mass shooting in the US' modern history, when a gunman stormed a gay nightclub in Orlando, Florida, killing 49 and injuring 58. Less than a month ago, on June 30, a doctor was killed and six people injured after a former physician opened fire inside a New York hospital.
Phillips' own views on gun control are that political labels have made consensus difficult, but that more people are aligned in their views than they realise.
"Most people would actually be in favour of waiting periods, background checks and ammunition clips that limit the number of bullets you can fire at a time or how quickly you can fire, which are some of the things that have made these attacks so horrible.
"I think it's absurd that we don't have more laws in place. Not that that would solve the issue, but there are some things that seem obvious, yet we can't seem to agree on enough to make them happen.
"Yet we go on through life. There's no way to live your life if you are constantly afraid."
•Fierce Kingdom by Gin Phillips is available at Books Kinokuniya for $27.82.