The bombers' social media pages were full of posts and suggestions about bombs and cruelty to Americans. It would have taken only one person to see some of these and think they had gone too far. These brother's were going to do something criminal against society eventually, and we decided not to stop them.
There is a lot of argument regarding safety issues and gun control. However, this attach was completely random, no matter how thought out and planned it was. I do not believe there was any way it could have been predicted or forseen. I do believe there have to be precautions in place that prevent such a horrible tragedy from happening to the best of our ability.
According to those who grew up with the boys, no one suspected they had anti-American feelings. I am sure that some things may have been said, but no one can predict whether or not a person is crazy enough to commit such heinous acts. Just because someone practices a certain religion does not automatically mean that they are a terrorist. There are extremists in every religion and unless you are a member of that group, you cannot predict who is willing to murder others in the name of their faith.
We don't go to events expecting someone to bring a bomb. Unless you are a psyhic, there is no way to predict something will go wrong. We don't know what is going on through people's minds. After the 9/11 attacks, we began taking extra precautions. However, precautions does not equal foreseen.