Investigators are still waiting to interview Boston Marathon bombing suspect Dzhokhar Tsarnaev, whose wounds reportedly include gunshots to his neck and leg. An official tells CNN that Tsarnaev was "intubated and sedated," rendering him unable to speak with them.
Massachusetts Gov. Deval Patrick described Tsarnaev's health Saturday as "serious but stable... I think, not able to communicate yet."
Officials are developing ideas about the possible motives of Tsarnaev and his older brother and fellow suspect Tamarlan Tsarnaev, who died after a gunfight with police. They also want to know if the two suspects acted alone when they allegedly planted bombs near the marathon's finish line.
Another question being asked is whether the attacks could possibly have been prevented.
As we've reported, the FBI acknowledged Friday that its agents interviewed Tamarlan Tsarnaev in 2011, after being asked by a foreign government to investigate him as a potential risk. The FBI says it was told that Tsarnaev was "a follower of radical Islam and a strong believer, and that he had changed drastically since 2010 as he prepared to leave the United States." The FBI's inquiry did not uncover any terrorist activities.
The FBI did not identify the foreign government in an official statement, but the AP and other news outlets have identified it as Russia, a country Tamarlan Tsarnaev visited several times. The Tsarnevs are ethnic Chechens, "with links to the volatile North Caucasus region of Russia," as NPR's Corey Flintoff reported Saturday.
A senior congressional aide tells The Boston Globe that members of Congress are asking law enforcement officials about the FBI's earlier investigation of Tsarnaev.
"The FBI had this guy on the radar and somehow he fell off," the aide says. "We heard for several days leading up to this there was no intelligence. Now we know there could have been intelligence."
In Boston, the site of the twin attacks is still being processed for evidence. Nearby, mourners and well-wishers have left a pile of flowers, notes and mementoes in the days since the attack.
An interfaith memorial service is planned for 12:30 p.m. ET Sunday at the intersection of Boylston and Berkeley streets, where the members of six churches are gathering to honor the attack's victims.
We'll update this post as news about the attack and the suspects develops today.
Update at 1:20 p.m. Boston PD chief says suspects may have planned more violence:
The Tsarnaev brothers had enough weaponry to inflict more damage, Boston Police Commissioner Ed Davis says of the marathon bombing suspects.
"We have reason to believe, based upon the evidence that was found at that scene... the explosive ordnance that was unexploded, and the firepower that they had, that they were going to attack other individuals," Davis said on CBS's Face the Nation Sunday. "That's my belief at this point."
"They had IEDs, they had homemade hand-grenades that they were throwing at the officers," Davis said. "The scene was littered with unexploded improvised explosive devices that actually, we had to point out to the arriving officers and clear the area. They were strewn about the area. There was also one found in the motor vehicle that was abandoned, the Mercedes SUV."
Update 11:23 a.m.: Hundreds gather for Boston memorial service near marathon's finish
Hundreds of Boston-area residents gathered Sunday to pray, to sing, and to memorialize the victims of bombs and other violence in the city this week. Six churches organized an interfaith service near the intersection of Boylston and Berkeley streets, close to the cordoned-off area where investigators are examining the crime scene created when bombs tragically altered the finish of the 2013 Boston Marathon.
At the memorial service held six days after police say suspects Tamerlan and Dzhokhar Tsarnaev began a spree of violence, residents celebrated the victims of the bombing attack, and proclaimed themselves free from the anxiety that gripped the area during an intense manhunt for the two brothers that ended Friday night.
The event began with a moment of silence in honor of the more than 170 people who were wounded in the bombing, as well as three people who died Monday — Martin Richard, 8; Lu Lingz, 23; Krystle Campbell, 29 — and MIT Police Officer Sean Collier, 26, who was slain Thursday night.
The crowd filled the intersection where a makeshift memorial of flowers and messages has grown in the days since Monday's bombings. Several of those in attendance held signs evoking the message "Boston Strong," and thanking the area's police departments for their work in securing the region and making an arrest in the case.
Boston's WCVB carried a live blog of the event, including a running account by that station'sSean Kelly of the songs sung by the crowd:
A more formal memorial service was held Thursday morning, an event that was organized by the office of Gov. Deval Patrick. That interfaith service was attended by President Obama, as well as former Massachusetts Gov. Mitt Romney.
Update at 9:47 a.m. Boston.com's video recap of the week's events
Boston.com has put together a video montage of events of the past week, beginning with the opening of the Boston Marathon.
Update at 9:20 a.m. ET. Bomb Suspects Acted Alone, Mayor Says:
Menino provided no details about the health of suspect Dzhokhar Tsarnaev other than to say, "we don't know if we'll ever be able to question the individual."
When reminded by ABC's George Stephanopoulos that Massachusetts does not have the death penalty as an option, Menino said, "I hope that the U.S. attorney, Carmen Ortiz, takes him on the federal side and throws the book at him."
Update at 6 a.m. ET. London Marathon Marked By High Security, Memories Of Boston:
The London Marathon observed 30 seconds of silence before the race got under way Sunday, in a show of solidarity with those injured in Monday's Boston Marathon. Many runners wore black ribbons to honor the three people killed and the more than 170 injured in two bombings in Boston.