On June 17, 2015, U.S. Sen. Tim Scott had dinner with Congressman Trey Gowdy — because that's what they always did.

They talked. They ate. And the two South Carolina Republicans did something rare in Washington: They trusted each other.

Two hours later, after the two parted ways, Scott's phone rang.

"Tim," the voice on the other end of the line said, "there's been a shooting in Charleston. It's Clementa Pinckney's church."

Scott's mind began to race as more details came out:

A shooting at Charleston's Emanuel AME Church.

A shooting where my friend Clementa preaches. 

A shooting where the shooter was white and the victims were black.

A shooting motivated by race.

Without thinking, Scott texted Pinckney to ask if he was OK. Silence. Then he speed-dialed Gowdy.

"I was heart-in-hand devastated," Scott told The Post and Courier on Thursday. "But for me to reach out to a white guy after Mother Emanuel, that's just a testament to how much things have changed in South Carolina and how much things can change."

Scott, who is black, was raised in North Charleston by a single mother who worked as a nurses' aid. Gowdy, who is white, grew up in an affluent area of the Upstate as the son of a doctor. And yet the two became friends after arriving in Congress in 2010.

Now, Gowdy and Scott have written a book about how unexpected friendships like theirs could be the key to reconciliation during a deeply polarizing time in America.

"Unified: How Our Unlikely Friendship Gives Us Hope for a Divided Country" is set to be released Tuesday from Tyndale House Publishers. The company is considered one of the largest privately held Christian publishers of books, Bibles and digital media in the world.

"The tendency to highlight what you don't have in common, as opposed to what you do, has existed since the day I set foot in Washington," Gowdy said. "But I really do think people are hungry for something else."

The two began writing the book in March 2017. To commemorate the moment, Scott posted a photo of them to his Instagram account with a caption that said he was working with Gowdy on a project for 2018.

"Most people mistook it to mean he (Scott) was running for governor," Gowdy said, laughing.

Fun Saturday with @tgowdysc working on a project for 2018!

A post shared by Senator Tim Scott (@senatortimscott) on

Gowdy, who in January announced he would not seek re-election for his seat in the Greenville/Spartanburg-anchored 4th Congressional District, said writing the book became a weekend project of his. It also became an activity that helped him realize it was time to leave Washington for good.

"The whole Benghazi experience sucked the life out of me," Gowdy said of the probe into the attack against the U.S. consulate that left four Americans dead and would focus on Secretary of State Hillary Clinton's response.

"I have no appetite in running another investigation in Congress," he added.

Gowdy said he would have left Congress sooner, but he ran for office again in 2016 because Scott asked him to stay.

Both Gowdy and Scott are Republicans, but their upbringing has resulted in different perspectives. It's why the book pivots between sections written by Gowdy and sections written by Scott.

The two lawmakers said it is also why they decided to include two separate chapters on law enforcement.

"Trey has a bias toward law enforcement. I have a healthy respect for them, but I also have a more tension-filled experience with them," Scott said, who in his chapter writes about his experiences of being racially profiled.

Gowdy, by contrast, writes about Spartanburg sheriff's Deputy Kevin Carter, who was shot and killed in 2007 in pursuit of a suspect who fled the scene during a traffic stop.

"I hope the country benefits from seeing this transparency and vulnerability. It wasn't easy or comfortable, but it felt necessary," Scott said of writing those chapters.

Neither Gowdy nor Scott said they expect their book to become a major political best-seller, but that's not why they wrote it.

"As we've learned since the election, the Russian meddling in our elections was not at the ballot box but in trying to sow seeds of discord and erode a unified America. That division, I did see it before, but I see it now as a vulnerability with national security implications," Scott said.

Conflict sells, Gowdy said, but it's not what heals.

"I have faith that anger is exhausting and at a certain point in any relationship you look at each other and say, 'You know what? I'm tired of fighting,' " Gowdy said. "And that's the thing. Through it all, Timmy and I have prioritized our friendship."

The two will hold four events in South Carolina to promote the book. 

Reach Caitlin Byrd at 843-937-5590 and follow her on Twitter @MaryCaitlinByrd.

Caitlin Byrd is a political reporter at The Post and Courier and author of the Palmetto Politics newsletter. Before moving to Charleston in 2016, her byline appeared in the Asheville Citizen-Times. To date, Byrd has won 17 awards for her work.