Dzhokhar Tsarnaev was charged today with using a weapon of mass destruction in last week’s bombing of the Boston Marathon, but his condition is preventing him from answering investigators’ questions:

The full extent of Tsarnaev’s injuries, and whether he sustained them in a gun battle with police early Friday, remains unclear. He has a gunshot wound to the neck, Boston police said Sunday, and federal and local officials say they do not know whether he will be able to talk again.

If convicted, Tsarnaev could face the death penalty. The complete account of the bombing and the investigation that followed is here. The attacks demonstrated the limits of law enforcement and military efforts to foil terrorist plots, observers said:

The United States has spent billions of dollars on counterterrorism efforts. . . . Overseas operations have pushed al-Qaeda to the brink of collapse, and domestic steps have dramatically reduced the country’s exposure to an attack of the scale and sophistication of Sept. 11.

But the Boston bombings highlighted a lingering vulnerability that officials consider impractical, if not impossible, to eliminate. It centers on small-scale plots carried out by individuals who are unlikely to surface on federal radar. They rely on devices made from common ingredients such as gunpowder, nails and a pressure cooker. They target public gatherings where security resources are stretched. (Read the rest of the analysis here.)

See the full sequence of events in the aftermath of the Boston Marathon bombings.

Yet fears of a similar attack did not deter participants in the London Marathon yesterday:

In the wake of the Boston attacks, Scotland Yard deployed several hundred more officers to ramp up race-day security and reassure the public. More than 650,000 people were expected to watch 36,000 runners traverse the iconic course that snakes its way from leafy Greenwich Park to the finish line on the Mall, a wide boulevard leading to Buckingham Palace.

A few here expressed lingering safety concerns. But on a sunny spring morning very similar to last week’s fateful day in Boston, London appeared largely able to push aside any sense of fear, with many in the crowd embracing a light-hearted, even festive mood. Men running for charities wore dresses and pink wigs. Women were decked out in blue tutus, and the Beach Boys’ “Good Vibrations” blared over the sound system as runners stretched and warmed up. (Read more from London here.)

In Boston as well, many were putting the week’s events behind them, writes Ibby Caputo, who lives on the same street where the Tsarnaev brothers did:

By Saturday morning, it was as if nothing had ever happened here. No police presence. No international media camped out at the end of the street. The only remnants of Friday’s crime scene were a few police barricades pushed against a brick wall.

In a cafe, I overheard a few people talking about Friday’s events, clarifying for one another the facts as far as anyone knew them. No one seemed particularly shaken up. Mothers walked by with babies in strollers, people were out walking their dogs, and the Portuguese-speaking men were swapping stories on the sidewalk as usual. The fish market had customers, and shovels lined the outside of the hardware store on Norfolk Street, open for business. (Read the rest of Caputo’s essay here.)

You can view the criminal complaint against Tsarnaev from the Department of Justice here.