Good morning, NBC News readers.

Big tech’s role in spreading extremism is coming under scrutiny — again — in the wake of the New Zealand shooting massacre. The Midwest is bracing for more flooding after a 'catastrophic' deluge in Iowa and Nebraska.

And meet a charming 8-year-old refugee who is also New York State's reigning chess champ for his age group.

Here's what we're watching today.

Can social media companies control the spread of hate?

The dissemination of a video across the internet apparently recorded by a shooter who killed 50 people at two mosques in New Zealand has reignited debate around how tech companies moderate their platforms — and whether they've done enough to crack down on the spread of hate online.

Critics say that companies like Facebook and YouTube have not done enough to address white supremacist groups on their platforms. Others counter that pushing tech companies to further regulate extremism will not fix the deeper problems of online radicalization.

New Zealand's Prime Minister Jacinda Ardern vowed that her government will take a look at the role social media may have played in the massacre.

"They are the publisher, not just the postman," Arden said during a passionate speech to Parliament on Tuesday. "There cannot be a case of all profit, no responsibility."

'Unbelievable' flooding in the Midwest — and more to come

Vast stretches of the Midwest remained threatened by what the National Weather Service described late Monday as "major to historic" flooding, even as officials and residents grappled with a recent deluge that left three people dead in Iowa and Nebraska.

Flood warnings and advisories remained in effect across the Plains, the Mississippi Valley, and parts of the Ohio Valley region, the weather agency said.

The roof of the Bluff View Motel is seen during the flooding of the Missouri River near Glenwood, Iowa, on Monday. Passport Aerial Photography / Reuters

What would the founding fathers have thought of Trump owning a luxury hotel next to the White House?

A federal appeals court will hear arguments today on a challenge to President Donald Trump's ownership of a luxury hotel five blocks from the White House.

It's the highest level hearing yet on lawsuits claiming that his vast holdings present a conflict between his business profits and the nation's interest.

A central question is what the term "emoluments" means. Legal scholars have conflicting views on what the founding fathers intended when they added the clause to the Constitution.

Plus

The man suspected of gunning down a New York City mob boss appeared in court Monday with the phrases "MAGA Forever" and "United We Stand MAGA" scrawled across his left hand.

'Devin Nunes' Mom' may be a parody Twitter account, but it's no laughing matter to the Republican California representative. He's suing Twitter and several of its users for more than $250 million, accusing them of defamation and negligence.

USC students tied to the college admissions scandal can't enroll in classes or get transcripts until their cases are reviewed, the university said.

Don't discount these six possible March Madness Cinderella teams.

Science + Tech = MACH

Could artificial intelligence help catch shoplifters before they act? One tech startup says they've developed software that could identify suspicious activity based on a shoppers' body language, gait and facial expressions.

Live BETTER

What can you do about tackling climate change and pollution in your daily life? Here are eight simple ways to reduce plastic use.

Quote of the day

"He is a terrorist. He is a criminal. He is an extremist. But he will, when I speak, be nameless. And to others I implore you: speak the names of those who were lost, rather than name of the man who took them."

— New Zealand's Prime Minister Jacinda Ardern on the suspect in the terror attacks that killed 50 people at two mosques in Christchurch.

One fun thing

Meet the 8-year-old Nigerian refugee who is also a budding chess star.

Tanitoluwa Adewumi, a homeless third grader, just won the New York State chess championship for his age group – even though he only picked up the game a year ago.

“What I like the most about chess is deep thinking,” says Tani.

His family came to New York from Nigeria two years ago —fleeing persecution by Boko Haram terrorists on Christians like themselves. His dad works two jobs and his mother just passed a home health care course, but they live in a homeless shelter.

Since his big win there has been a huge outpouring of support – from a New York Times article to a GoFundMe page for Tani that’s raised over $100,000.

His parents have been stunned by the generosity of the city and country where they prayed to find refuge. “I’m so proud of him,” says his mom.

Thanks for reading the Morning Rundown. If you have any comments — likes, dislikes — drop me an email at: petra@nbcuni.com

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Thanks, Petra