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

From exercise to emails, see the stories we're following today.

Good morning. Here are some of the stories we’re following today:

1. Biker brawl could have stemmed from jacket patch battle

Five biker gangs were involved in Sunday's violence at a Texas restaurant that left nine people dead and dozens arrested, but the main fight was between two gangs — the Bandidos and the Cossacks, experts said. The fight was allegedly over the Cossacks' plans to include a reference to Texas on the lower section of its official jacket patch, which points to a bigger turf war between the gangs in the state, according to experts. Read more in NEWS.

2. Iraq’s fight against ISIS faces serious challenges

The Iraqi army had loose goals of pushing ISIS out of the country by the end of the year, but the fall of Anbar province's main city of Ramadi to the militant group puts offensive actions on hold. Iraqi security commanders will meet on Tuesday to pull together outlines of the new plans to liberate Ramadi, in coordination with the U.S.-led coalition. Read more in NEWS.

3. Derailed Amtrak train doesn’t show gunshot evidence

The FBI has found no evidence of damage caused by a firearm on the windshield or engine of the Amtrak train that derailed in Philadelphia last week, according to the NTSB. Investigators said they haven't ruled out that another object may have hit the train before it crashed. Read more in NEWS.

4. What’s the fittest city?

The American College of Sports Medicine ranked Washington, D.C., as America's fittest city, largely because residents have easy access to exercise and healthy food. Last place went to Indianapolis, with Memphis scoring barely any better. Read more in HEALTH.

5. Hillary Clinton emails will be released in early 2016

The State Department said it needs until the end of the year to review the 55,000 pages of emails from former Secretary of State Hillary Rodham Clinton before releasing them to the public. The disclosure that Clinton conducted State Department business on a private account has been controversial since the beginning of the presidential candidate's campaign. Read more in NEWS.

6. Is the Osprey safe? Pentagon says it is

The Defense Department said it would not decrease use of airplane-helicopter Osprey aircrafts after a Marine was killed and 21 others were injured in a crash at Bellows Air Force Base, Hawaii. At least 30 people were killed in several crashes during the testing phase of the Osprey, but officials say it's now reliable. Read more in NEWS.

7. 14 charged with trafficking drugs through airport

Three Southwest baggage handlers and 11 others were arrested for a three-year-long scheme to ship marijuana from state to state by taking advantage of security clearances. The defendants were charged with conspiracy to distribute and possess with intent to distribute 100 kilograms or more of marijuana. Read more in NEWS.

8. Nightly Spotlight: ‘Empathy cards’ tell it like it is

Emily McDowell, a greeting card writer and designer, has decided to leave platitudes out of cards for people battling cancer and other diseases. Instead, she sells cards that say things like: "Let me be the first to punch the next person who tells you that everything happens for a reason."