I know exactly when my life changed: when I looked into the face of Tamerlan Tsarnaev. It was 2:48 p.m. on April 15, 2013—one minute before the most high‑profile terrorist event on United States soil since September 11—and he was standing right beside me.

We were half a block from the finish line of the Boston Marathon, two in a crowd of half a million. The marathon was the signature event of Patriot’s Day, Boston’s special holiday, which celebrates Paul Revere’s ride and the local militiamen who fought the first battle of the American Revolution on April 19, 1775. Patriot’s Day was also the unofficial start of spring, in a city known for brutal winters, so half the city had taken the day off, and everyone wanted to be outside. By tradition, a Red Sox home game had started at 11:00 a.m., coinciding with the last starting group of the marathon. By 2:30, baseball fans were pouring out of Yawkey Way onto Boylston Street, swelling the marathon crowd.

I had arrived half an hour earlier, with my friends Remy and Michele, to cheer for my girlfriend, Erin Hurley. Even then, the side‑ walks were clogged ten deep, and the restaurants and bars were filled with people in Red Sox gear and Boston shirts. The best runners, who qualified for the first start time, had finished hours before, but the runners kept coming, and the crowd kept growing. Most of these people, including Erin, were running for charity. They were the average run‑ ners, the ones who needed and deserved our support. Everywhere I looked, people were cheering and clapping, yelling for them to keep going, the finish line was close, they were almost there.

And then I noticed Tsarnaev.

I don’t know how he got beside me. I just remember looking over my right shoulder and seeing him. He was standing close, maybe a foot away, and there was something off about him. He was wearing sunglasses and a white baseball cap pulled low over his face, and he had on a hooded jacket that seemed too heavy, even on a cool day. The thing that really struck me, though, was his demeanor. Everyone was cheering and watching the race. Everyone was enjoying themselves. Except this guy. He was alone, and he wasn’t having a good time.

He was all business.

He turned toward me. I couldn’t see his eyes, because of his sunglasses, but I know he was staring at me. I know now he was planning to kill me—in less than a minute, he thought I’d be dead—but his face revealed no emotion. No doubt. No remorse. The guy was a rock.

We stared at each other for eight, maybe ten seconds, then my friend Michele said something, and I turned to talk to her. Our friend Remy had moved toward the finish line to try to get a better view. I was about to suggest to Michele that we join her. That was how much this guy bothered me.

But I didn’t. And when I looked back, he was gone.

Excerpted from the book Stronger by Jeff Bauman with Bret Witter. Copyright © 2014 by JB Liege, LLC. Reprinted by permission of Grand Central Publishing. All rights reserved.