During his remarks on Oct. 2 after the Las Vegas shooting, President Trump quoted from the book of Psalms. (The Washington Post)

President Trump departs from the habits of his predecessors in many ways, but not in this one: In his Monday speech after the deadliest mass shooting in modern U.S. history, Trump used biblical language to comfort Americans trying to make sense of the tragedy.

“Scripture teaches us the Lord is close to the brokenhearted and saves those who are crushed in spirit,” Trump said, quoting the book of Psalms. “We seek comfort in those words, for we know that God lives in the hearts of those who grieve.”

Recent reports have highlighted that the percentage of Americans who are Christian is declining: In 1990, the number of Christians in the United States was 86 percent, according to the American Religious Identification Survey. That number is now 70 percent. And since the early 1990s, the percentage of Americans identifying as “atheist,” “agnostic” or “nothing in particular” has roughly tripled in size.

These changes are threatening some Christians' understanding of America as a whole, particularly older, white Christians.

“Falling numbers and the marginalization of a once-dominant racial and religious identity — one that has been central not just to white Christians themselves but to the national mythos — threatens white Christians’ understanding of America itself,” Robert J. Jones, author of “The End of White Christian America,” previously told The Washington Post.

Christianity is still the dominant religion among the three largest races in the United States, according to the Public Religion Research Institute. While 69 percent of white Americans identify as Christian, 75 percent of black Americans do. Latino Americans have the highest percentage of Christians (76).

While America may be becoming more religiously diverse, all of its presidents since Abraham Lincoln have been Christian. Ties between certain religious identity groups and political parties remain important in the United States. Nearly three in four (73 percent) Republicans belong to a white Christian religious group. And more than two-thirds (68 percent) of black Protestants identify as Democrats.

But that could change given the country's growing religiously unaffiliated population. Nearly 6 in 10 — 58 percent — Americans said they would have voted for an atheist president — four percentage points higher than in 2012, according to Gallup.

Despite the changes, when the country suffers a tragedy, many Americans look to the president for some sort of comfort — including spiritually.

On Monday, Trump, whom Focus on the Family founder James Dobson has called “a baby Christian,” gave remarks marked by religious language and tenets of the Christian faith:

“Melania and I are praying for every American who has been hurt, wounded, or lost the ones they love so dearly in this terrible, terrible attack. We pray for the entire nation to find unity and peace. And we pray for the day when evil is banished and the innocent are safe from hatred and from fear.

May God bless the souls of the lives that are lost. May God give us the grace of healing. And may God provide the grieving families with strength to carry on.”

Trump looked to the language of the Christian faith to step into his role as “comforter in chief,” a move consistent with many presidents. After the 2011 shooting of Rep. Gabrielle Giffords (D-Ariz.) in Tucson, President Barack Obama referenced the biblical story of Job, a man who endured suffering that included the loss of his family, to help Americans remember that horrible things happen for reasons that aren't always clear.

“Scripture tells us that there is evil in the world and that terrible things happen for reasons that defy human understanding,” Obama said. “In the words of Job, 'When I looked for light, then came darkness.' Bad things happen, and we have to guard against simple explanations in the aftermath.”

“Simple explanations” appear to be elusive in the aftermath of the Las Vegas shooting. Law enforcement said the shooter left no clear answer as to why he killed at least 58 people and injured hundreds.

Especially when facts were not fully known, recent U.S. presidents have looked to Christian texts to offer some level of clarity. On the night of the Sept. 11, 2001, attacks, President George W. Bush turned to the Psalms.

“Tonight, I ask for your prayers for all those who grieve, for the children whose worlds have been shattered, for all whose sense of safety and security has been threatened,” he said. “And I pray they will be comforted by a power greater than any of us, spoken through the ages in Psalm 23: ‘Even though I walk through the valley of the shadow of death, I fear no evil for you are with me.’ ”