I got back to my room late, after a long dinner with a friend. I’d been teaching all week at the University of Wisconsin in Madison; I’d spoken to three classes and three groups in a 12-hour day, and I was wrung out and ready to sleep. But I picked up my phone first. As you do; as we all do, now.

I spotted tweets from my friends Tom Levenson, a writing professor at MIT, and Paige Williams, a writing instructor at Harvard. There was a shooting at an MIT building. There was a death.

Oh no, I thought. I knew exactly where that was. I worked in Boston for 5 years, had colleagues everywhere there, had gone to programs at MIT, had watched skeptically as the crazy, faceted Stata building went up. Now a photo from within the building showed a pool of blood at the base of it. My news sense — a thing that reporters develop over years, mock and deride, but rely on — tingled uncomfortably. This was not normal, for this corner of Cambridge. It might be random. But it might be connected to the marathon bombing. Suddenly I wasn't sleepy at all.

I noticed Seth Mnookin, another friend and MIT instructor, was tweeting reports of shots and explosions carried by the local police scanner channels. Reporters always want to hear things for themselves; I found the page and tuned in too. Then Seth and Taylor Dobbs, a fierce journalist and son of my Wired colleague David Dobbs, announced they were heading out to the scene.

I've spent plenty of time at crime scenes and disasters. I figured it would be loud, chaotic, bandwidth-sucking. Selfishly, I thought I was losing my information source. Then I thought, maybe I can help. I took up the task they'd been performing, relaying details from the Boston scanner. The first report I focused on captured the confusion: “All units retreat, retreat.”

I started live-tweeting what I heard.

Power down all cell phones for fear of explosion.”

”Officer missing on Spruce Street.” “We got him!

We have the vehicle. The vehicle has been cleared.”

My awareness narrowed to the voices rasping out of the speaker, the keys clicking on my laptop, Seth and Taylor's thumbed descriptions flowing down the page.

Voices piled on voices, barking, warning, whispering. The suspect was the bomber, the kid in the white hat from the marathon finish line. The suspect was armed and extremely dangerous. The suspect was on the run.

On the screen, people pushed along my tweets, made comments and guesses, started to verify and amplify, and distort. That worried me, so I edited as I transcribed. A commander called out streets they were racing to and houses they were searching. I redacted the addresses. A team forced a possible suspect into a squad car, spelled out his name and read out his ID card; I reported there was a name and a birth date, but not what they were. The cops asked a copter pilot to focus his headlights on a back yard where the bomber might be hiding. I froze my fingers, waiting to draw attention to the copter until the pilot warned the fog was too thick for him to stay up there for long.

After four or so hours, the pace of the chatter slackened. The cop voices summoned the media to a briefing in a secured area of Watertown. Seth and Taylor reported the crush of cars and cameras was dissolving; they were barred from Seth's vehicle, stuck on the wrong side of the secure zone, looking for a ride home. I stretched my shoulders, told my new followers I needed a break, looked at the 100 tweets I had written, spotted the first quick thank yous before I closed the lid.

I remembered tuning in the police radio in the old Boston Herald newsroom, listening for anything urgent enough to send the photographers running before the presses rolled after midnight. I thought how isolated it had felt, leaning against a lumpy pile of newsprint under the buzzing fluorescents, wondering who else was straining to hear through the shouts and crackles. I was grateful, this time, not to have done it alone.