Steffen Kaplan, a social media specialist in New Jersey, tried his best to protect his young son from the madness. His television stayed off. He browsed the Internet with caution. But reality finally intruded at a local pizzeria, where a TV was playing images of the injured in Boston.

“What’s going on?” his son asked. “Nothing,” Kaplan replied. “That’s just a movie.”

Kaplan fears the world his son will inherit. To cope, “I rely on faith in humanity,” he said. “If we raise our children correctly, somehow, some way, humanity will prevail.”

But the present remains difficult, Kaplan said: “It seems to be a spiral of things happening one after the other. It can be inundating on your senses.”

The downward spiral steepened Tuesday morning. As authorities in Boston searched for leads, and the nation debated whether the perpetrators were terrorism or a different type of killer, congressional leaders said a letter containing the poison ricin had been mailed to Sen. Roger Wicker of Mississippi. It touched off memories of the jumbled days after 9/11, when letters containing anthrax were sent to politicians and media organizations..

On Wednesday, the Secret Service said it had intercepted a ricin letter mailed to President Barack Obama. Tensions immediately rose in Washington, with a half-dozen suspicious packages reported and parts of the Capitol complex shut down. On Wednesday evening, a suspect was arrested in Mississippi.

“I think it’s fair to say this entire week we’ve been in pretty direct confrontation with evil,” Secretary of State John Kerry said.

All this happened as the Senate, with high feelings on both sides, voted down legislation that would have banned assault weapons and expanded background checks of gun buyers. The measures, sought for decades, only became possible after 20 children and six others were gunned down at Sandy Hook elementary school in Newtown, Conn.

The defeat of the bill “brought the whole Sandy Hook thing up again,” said Rachel Allen, a lawyer from suburban Pittsburgh.

“There are so many senseless things that go on, and you see how people can come together,” Allen said Friday. She recalled being moved to tears watching the first Boston Bruins hockey game after the bombing, when the national anthem singer fell silent and let the entire arena roar the song to a finish.

Events in Washington can magnify the sense of chaos, says Fischoff, the psychologist. “Most of our institutions that we use to stabilize ourselves and our country are damaged, crippled,” he said. “What you’re having is a kind of emotional, cognitive anarchy.”

Late Wednesday night, reports emerged of an explosion outside Waco, Texas. As Thursday dawned, the magnitude became clear: A fertilizer plant had blown up with such force, it registered as an earthquake and wrecked homes, apartments, a school and a nursing home. As of Saturday morning, 14 people were dead.

“Is this week feeling a little apocalyptic to anyone else?” tweeted Jessica Coen, editor in chief of the Jezebel.com blog. “Boston. Poison. Explosions. Floods. Tomorrow, locusts.”

Recent Aprils have often been cruel to America. In 1993, dozens died in the siege of the Branch Davidian compound in Waco. In 1995, a domestic terrorist killed 168 people in the Oklahoma City federal building bombing. In 1999, two students killed 12 classmates, a teacher and themselves at Columbine High School. In 2007, a student rampage left 32 innocents dead at Virginia Tech.

But April 2013′s convergence of events is extremely rare, statisticians say.

Such calculations are based on the likelihood of each individual tragedy, said Michael Baron, a professor of statistics at the University of Texas at Dallas.

Baron has no actual data on how often this week’s events have separately occurred throughout history. But he estimated that if a terrorist attack occurs once every four years, a suspicious mailing once per year and an industrial accident twice per year, there is a .000004 probability of them all happening in the same week — “once in 4,808 years.”

Such absurd odds were too much for the satirical publication The Onion to resist.

The Onion “report” offered this “quote”: “‘Maybe next time we have a week, they can try not to pack it completely to the (expletive) brim with explosions, mutilations, death, manhunts, lies, weeping, and the utter uselessness of our political system,’ said basically every person in America who isn’t comatose or a complete sociopath.’”

The week was no joke for Mary Helen Gillespie, a bank vice president who lives near Boston. When she saw news of the Texas explosion, “I got sick to my gut.”

“If we were to look at a map of the United States right now — our country is strong and proud and brave and we will win. But if you look at a map, we are bleeding,” Gillespie said.

“The world is upside down,” she said. “Facebook can’t keep up with it, TV can’t keep up with it. It’s just overwhelming.”

“What I found was hope in prayer,” Gillespie said. “The more the media started reporting on the stories of hope, the heroes, the first responders, the everyday Americans going out trying to save others. That was my inspiration. It was, OK, this will get better.”

While authorities tried to determine Thursday how many had died in the fertilizer plant explosion — many victims were feared to be first responders who rushed into the inferno — the FBI released photos and videos of two suspects in the marathon attack.

“It’s been a rough week for the country,” said House Majority Leader John Boehner. “It’s been a rough week, but we’re thankful for the blessings of life and the opportunity to live in a country whose people always look out for each other.”

Finally, on Friday morning, the nation awoke to news that one suspect and a police officer had been killed — after the suspects hurled explosives during a car chase and had a shootout in the residential community of Watertown.

In Chicago, the cover of the Redeye newspaper on Friday was a giant red RESET button. “That was a rough one. Who’s ready for next week?” the caption said.

Jesse Bonelli, a video game artist who lives in locked-down Watertown, stayed inside his house Friday and sharpened a machete — just in case.

“It’s something I usually keep hanging on the wall, but it’s the only weapon I have,” he said. “I want to be ready in case anyone bursts into the house. After everything that happened this week, I keep wondering what’s next.”

All day Friday, Boston was shut down, public transit halted and people ordered to stay in their homes as thousands of police and federal agents chased down the fugitive.

He was finally captured on Friday night.

“God has not forsaken Boston. God has not forsaken our nation,” Rev. Miranda had said a few days earlier, at the prayer service. “He merely weaves a beautiful bright tapestry of goodness that includes a few dark strands.”

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Follow AP National Writer Jesse Washington on Twitter: http://www.twitter.com/jessewashington