With the exception of the 2009 mass shooting of 13 soldiers at Fort Hood, Texas, by a deranged Muslim major, this is the worst terrorist attack on a U.S. city since 9/11. But there have been at least 19 close calls, including the Underwear Bomber aboard an aircraft in 2009 and the thwarted Times Square bombing in 2010.
The lesson is that vigilance and preparation can greatly mitigate, though never completely block, a determined terrorist. The consolation is that this terrorist, or terrorists, almost inevitably will be caught.
Dale McFeatters writes for the Scripps Howard News Service.