People bear witnesss to the victims of Monday's bombing along the barricades on Boylston Street in Boston on Tuesday. (Getty Images / April 16, 2013)

What say everyone go to the Boston Marathon next year, to cheer the runners on, support the city and simply make a statement about what kind of society we want to have?

That is a society that holds great outdoor celebrations that people can attend without risking their lives.

Tragically, that was not the case for the 117th running of the Boston Marathon on Monday, when bombs planted near the finish line killed three people, including an 8-year-old boy, and injured more than 180.

In some parts of the world, roadside bombs and other violent attacks are a part of life. For a long time, that was not the rule here, despite our extraordinarily open society. That age of innocence, that charmed life, ended on Sept. 11, 2001, in New York City. Since then, at least 50 terrorism plots have been foiled by U.S. counterterrorism efforts, according to the Heritage Foundation, which tracks thwarted attacks.

To the Boston runners who were in New York during 9/11 and the Newtown contingent at the race who had endured the unthinkable mass murder of children and women on 12/14, it must seem like the U.S. is becoming Syria or Iraq. It isn't, but the trend isn't good, and that's why everyone needs to pay more attention.

If the U.S. is forced to become one large gated community, then the terrorists achieve their goals. That cannot happen. But it means that an alert citizenry has to keep an eye out for the potentially dangerous, and tell somebody. It means better mental health screening. It means going to events such as the Boston Marathon.

It's still not clear who perpetrated this sick and cowardly act, but as the world watched brave Boston police officers rush toward the explosions on Monday rather than away from them, we all felt pretty confident we would soon find out.