7 things to know now: 4 kids poisoned in Texas; what sank the Titanic; watch Mariah Carey's performance

Here's a roundup of news trending across the nation and world today.

What to know now:

1. Four children killed: Four children in an Amarillo, Texas, home were killed Monday when a poisonous gas was created when someone mixed water with a pesticide that had been placed underneath their home. The children, along with six others, were sickened when they were exposed to phosphine gas. The gas is believed to have been created when water was doused on a "restricted use” chemical -- aluminium phosphide -- that had been sprayed under the home to kill rodents, law enforcement officials said. Apparently, someone in the home complained about the smell of the pesticide, so waster was sprayed on the area, creating the noxious gas.

2. What sank the Titanic: According to a new study, a fire onboard the Titanic that burned below decks weakened the ship’s hull so badly that when the ocean liner struck an iceberg the ice had no problem ripping a hole in the ship. The fire, according to reports, started about 10 days before the ship left Belfast on its maiden journey. Thirty-foot-long black marks were reported along the hull behind where the iceberg gouged the ship late on the night on April 14, 1912.

3. Plans to repeal: According to Sean Spicer, Donald Trump’s incoming White House press secretary, the president-elect pans to “repeal a lot of the regulations and actions that have been taken by this administration over the last eight years that have hampered both economic growth and job creation." Spicer, speaking on ABC’s “This Week,” did not offer specifics on what would be repealed.

4. ISIS takes credit: The Islamic State on Monday claimed responsibility for the terror attack in Turkey over the weekend. According to a statement from ISIS, a "soldier of the caliphate" was the person who carried out the mass shooting at an Istanbul nightclub. Thirty-nine people were killed.

5. House votes Tuesday: The House of Representatives will vote Tuesday on a rules package, a day after Republicans voted to gut the Office of Congressional Ethics, putting what remains of the office under control of the House Ethics Committee. The independent body was created to investigate misdeeds by lawmakers. The package to be voted on also includes a process for House leaders to punish lawmakers for such actions as the Democratic sit-in over a gun control vote that took place last summer. 

And one more

Dylann Roof, who killed nine people as they prayed in a South Carolina church in June of 2015, is competent to represent himself as he moves into the penalty phase of his trial, a judge ruled Monday. Roof says he will call no witnesses and present no evidence as a jury decides whether he will be sentenced to die or spend the rest of his life in prison. Prosecutors say they will call 38 people related to the nine killed at the Emanuel AME Church in Charleston, in addition to calling three survivors of the shooting.

In case you missed it

Here's the Mariah Carey performance everyone has been talking about.

WATCH: Mariah Carey's New Year's Eve mishap; what really happened during performance? https://t.co/tEnHkiVXyy pic.twitter.com/iv4mw01njt

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