Yesterday at 3 p.m., my colleague looked up from his iPhone. “There was some kind of explosion at the Boston Marathon.” He immediately went to his computer and pulled up a news site. A banner ran across the page. Breaking: Two explosions at the Boston Marathon. No other information. I pulled up the Drudge Report on my phone. Nothing on it. Then I went to Twitter. “Oh my god what just happened?” “We heard two loud booms at the finish line.” “My friend is running!” “Blood everywhere.” “Are we under attack?” “Chaos in #Boston.” The pictures were graphic and raw. Blood-drenched sidewalks. People crumpled on the ground. Medics and runners running into the smoke. A 5-second video showed the explosion itself, a burst of…