Confusion reigned in Watertown, Mass. late Thursday night after a campus police officer was shot and killed at MIT in nearby Cambridge. A carjacking followed by a massive police operation ensued in Watertown, with multiple reports of gunfire and explosions in several locations. At least one suspect is said by police to still be at large, armed and extremely dangerous.

UPDATE: Multiple police sources have stated that the shooters in tonight's incidents are strongly suspected to be the Boston Marathon bombing suspects.

The best place to follow the news as it unfolded: Twitter. Several reporters as well as residents were sending a stream of updates and pictures live from the scene. Herewith, in chronological order, shorn of all speculation and unconfirmed reports, is a curated selection of tweets that helped piece the story together.