Starting, of course, with the Boston Marathon bombing Monday. The bombers chose a significantly festive time and place for their attack.
The marathon is held every year on Patriots Day, the Massachusetts state holiday commemorating the Battles of Lexington and Concord in April 1775. Even before the identity of the bombers became known, it seemed likely that they were enemies of America.
And their attack was a reminder that this free and open country remains a soft target. There is no way we can be entirely safe.
If the marathon bombings brought back memories of the Sept. 11 attacks, the news on Tuesday and Wednesday that letters containing the poison ricin were sent to Sen. Roger Wicker and President Obama brought back memories of the anthrax-laden letters discovered the week after 9/11.
It was a comfort to see how well bystanders and first responders reacted to the marathon bombings and how law enforcement personnel, led by the FBI, were careful to avoid premature announcements.
Comforting also were Barack Obama's appropriate remarks in Boston on Thursday and the release by the FBI, after his departure, of photos of the two suspects.
Law enforcement invited the public to supply information and identify the killers. This contrasted favorably with the way law enforcement quarantined information about the Beltway snipers in October 2002.
But in the meantime, other things spun out of control.
On Wednesday, the Senate voted down gun control proposals, with the closest vote coming on the background check provision sponsored by Pennsylvania Republican Pat Toomey and West Virginia Democrat Joe Manchin.
In the Rose Garden, Obama spoke angrily and called the votes "pretty shameful." But they were an inevitable response to his cynical exploitation of the grief of parents of the Newtown victims to get votes for measures that would not have prevented that or other mass killings.
Obama made much of polls showing 90 percent support for background checks. But those polls didn't measure the response to arguments against those measures.
This was a test of Organizing for America, the offspring of the Obama presidential campaign. The idea is that OFA could pressure members of Congress just as it had turned out voters for Obama last fall.
But that ignored some relevant political numbers. The Obama campaign did motivate enough voters to carry 332 electoral votes. But those votes were heavily clustered in central cities and university towns.