When Krista Powell boarded a ferry at the southern tip of Manhattan early Sunday to head to the starting line of her first New York City Marathon, she expected to spend some quiet moments taking in the city’s skyline. Then she looked to her left.

There in the New York Harbor next to her ferry was a Coast Guard boat. On its bow was what several marathoners described as a machine gun, manned by a uniformed man who looked ready to shoot.

“It was kind of shocking, but then I remembered what happened in Boston,” Powell said, recalling the two bombs that went off near the finish line of the Boston Marathon in April, killing three people and injuring more than 260. “To see a huge gun on the boat next to us, that wasn’t expected. It was kind of drastic, but, unfortunately, it’s just what has to be done after people destroy an event for other people.”

This is the modern American sporting event, desperately trying to find a way to make big crowds safe crowds without letting armed forces steal the show. It isn’t easy.