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KNOW IT ALL: Tuesday's Top 6 Stories at NBC News

From a bloody synagogue attack in Jerusalem that left four dead to a deep freeze blanketing the U.S., see the stories we're following.

Good morning, and happy Tuesday. Here are some of the stories we’re following today:

1. Four dead in Jerusalem synagogue attack

A pair of Palestinians charged into a synagogue Tuesday in an ultra-Orthodox neighborhood and killed four people and wounded six others with knives and axes, Israeli police said. The suspects died in a police shootout, drawing praise from the militant group Hamas, which also called for more bloodshed. Secretary of State John Kerry condemned the violence amid reported rioting in an Arab neighborhood of East Jerusalem. Jerusalem Mayor Nir Barkat said authorities would “do everything in our power to restore peace and security.” Read more in NEWS.

2. Americans feeling a deep freeze

Nowhere’s safe from this bitter blast of arctic cold. Americans are waking up to a second round of freezing temperatures, with highs barely cracking the teens and 20s in the Upper Midwest and Great Lakes through the rest of the week. Other parts of the country will struggle to reach daytime highs in the 30s and 40s — temperatures that are more likely to be found in January rather than mid-November. (And yes, even Hawaii will see freezing temperatures, although those will be limited to the highest volcanoes.) Read more in NEWS.

3. Ebola doctor’s death is tough loss for West Africa

Dr. Martin Salia died Monday after arriving in the U.S. from his native Sierra Leone for Ebola treatment. The doctor was working as a primary care physician for a Methodist hospital, and wasn’t specifically working with Ebola patients when he became infected, officials said. His death is a setback in West Africa, where every skilled health care worker counts. Already, a number of prominent doctors have died from Ebola during this worst-ever outbreak of the virus. Read more in HEALTH.

4. Missouri governor declares state of emergency

With a grand jury decision due at any moment in the controversial case of Ferguson police officer Darren Wilson, Gov. Jay Nixon said Monday he was activating the National Guard in advance of any possible civil unrest. Nixon said he doesn’t believe there will be violence — but the move is a precaution after the shooting death of unarmed black teenager Michael Brown by Wilson already touched off a week of riots and looting this summer. The head of the NAACP, however, said a state of emergency only “threatens to stir up tensions.” Read more in NEWS.

5. Latest ISIS beheading raises more questions

When the terror network in Syria and Iraq releases a beheading video, they typically show the next hostage they intend to kill. But in the latest video featuring American Abdul-Rahman Kassig, there is no second hostage. The lack of one has terror analysts wondering what might have happened to the two known Western hostages captured by ISIS — and if U.S.-led coalition bombings have weakened the jihadists. Read more in NEWS.

6. Marley family rolls out its own pot brand

Bob Marley fans can enjoy more than just his music. Members of the late musician’s family have teamed up with a Seattle-based private equity firm to create Marley Natural, a line of cannabis-infused products. The goods — from cannabis itself to special creams — will be marketed with the help of the same agency that branded New Balance and Starbucks Coffee. The pot will be sold as “loose packed” buds, oils or concentrate, executives said. That means no pre-rolled joints — the kind that Marley was known for lighting up. Read more in BUSINESS.

And now this …

Scientists in Sao Paolo, Brazil, have a new weapon in the fight against cancer: tick spit. Tick spit has been shown to decrease the size of tumors while leaving healthy cells alone and could proceed to human trials soon.