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Elise Hu

This is a developing story. Last updated 9:12 a.m. ET.

Snipers shot and killed five Dallas law enforcement officers and injured another seven at the end of a rally in downtown Dallas, where hundreds were protesting police shootings that happened in other parts of the country earlier this week.

Four of the slain officers worked for Dallas Police; the fifth was identified as 43-year-old transit officer Brent Thompson, of Dallas Area Rapid Transit, or DART.

As I write this, snowstorms are swirling over the East Coast, threatening Thanksgiving holiday travel plans for millions of travelers. How much time in the purgatory of airports will this mean for you? Check out FlightAware's MiseryMap, which combines weather and flight data into a live map that lists which airports are being struck by storms, the number of delays and cancellations, and graphs that show flight destinations and the chances they'll actually make it on time.

Calm largely prevailed after a jury acquitted George Zimmerman Saturday night in the killing of Trayvon Martin. Law enforcement and community leaders had prepared for potential unrest, and riots had been feared for months. Slate's Dave Weigel sums up the fears: