Did you see it suspended under a bridge? Maybe it looked differently to someone who observed it there. And what does a bomb look like anyway? Is there one specific shape people should be concerned with? Of course not. I'm not familiar with bombs of any kind, so had I seen a strange gadget with wires and batteries, hanging from a bridge, which by the way tend to be targets of terrorists, I probably would have called it in myself.
I'm surprised at the hostility of the remarks on this thread aimed at Bostonians.
People who live in small towns in middle America have little understanding of life in NYC, DC, or Boston since 9/11.
The liberals in Boston will tell you that terrorism isn't a threat, it's a White house lie, but deep down they know that during the last scare Boston was one of the first two cities to have jets scrambled over them.