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KNOW IT ALL: Monday's Top 7 Stories at NBC News

The headlines include a furor over remarks by Donald Trump and a shark attack on live TV.

Good morning. These are some of the stories we're following at NBC News.

1. Scott Walker Calls for Donald Trump Apology

Gov. Scott Walker of Wisconsin, a Republican presidential candidate, is the latest to reject Trump’s assertion that Sen. John McCain is “not a war hero.” In an NBC News exclusive, Walker says even Trump’s supporters need to push him to apologize. Read more in NEWS.

2. Chattanooga Shooter Had History of Drug Abuse

Relatives and other people close to Mohammad Youssef Abdulazeez are beginning to piece together what might have motivated him to carry out an attack that left five members of the armed services dead. Read more in NEWS.

3. Pregnant Woman, Two Children Swept Away

The Midwest and Southeast face the threat of severe thunderstorms on Monday. In Ohio, surging floodwaters killed a woman who was six months pregnant, plus her 7-year-old son and 5-year-old daughter. Read more in NEWS.

4. Mother: ‘Time Stood Still’ During Shark Attack

The mother of a three-time world champion surfer was watching as he was attacked by sharks on live TV off South Africa. “I was absolutely terrified,” the mother says. “I thought we’d lost him.” Read more in NEWS.

5. U.S.-Cuban Diplomatic Ties Restored — First Time Since 1961

The Cuban flag is up at the State Department, and the diplomatic missions of each country have been upgraded to embassies. Secretary of State John Kerry plans to meet his Cuban counterpart on Monday, and they’ll hold a joint news conference. Read more in NEWS.

6. Cosby Detailed Womanizing Years Ago

In a deposition, Bill Cosby sketched a very different image of America’s Dad: a philanderer who plied young women with Quaaludes and tried to use his wealth to keep “Mrs. Cosby” in the dark. Read more in NEWS.

7. Researchers Look for Ways to Prevent Alzheimer’s

Researchers are working on tests to help predict Alzheimer’s disease years before people get symptoms, both to help them plan and in the hope that experimental treatments might work better the earlier they are used. Read more in HEALTH.