The surviving suspect in the deadly Boston Marathon bombing remained unable to speak with a gunshot wound to the throat, while the city's police commissioner said the two suspects had such a large cache of weapons that they were probably planning other attacks. Churches mourned the dead and consoled survivors Sunday.
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Authorities found many unexploded homemade bombs at the scene of the brothers' gun battle early Friday with police, along with more than 250 rounds of ammunition.
The stockpile was "as dangerous as it gets in urban policing," Boston Police Commissioner Ed Davis said. "We have reason to believe, based upon the evidence that was found at that scene — the explosions, the explosive ordnance that was unexploded and the firepower that they had — that they were going to attack other individuals," he told CBS.
Davis told Fox News that authorities cannot be positive there are not more explosives somewhere that have not been found. But he insisted the people of Boston are safe.
Investigators have not offered a motive for the marathon attack.
The suspects in Monday's twin bombings at the marathon finish line that killed three and wounded more than 180 are two ethnic Chechen brothers from southern Russia who had been in the U.S. for about a decade — 19-year-old Dzhokhar Tsarnaev and his 26-year-old brother, Tamerlan. Their motive remained unclear.
The older brother was killed in Friday's gun battle. The younger brother was still in serious condition Sunday after his capture Friday from a tarp-covered boat in a suburban backyard.
Authorities would not comment on whether he had been questioned.
Sen. Dan Coats, a member of the Senate Intelligence Committee, said Dzhokhar Tsarnaev's throat wound raised questions about when he will be able to talk again, if ever.
The wound "doesn't mean he can't communicate, but right now I think he's in a condition where we can't get any information from him at all," Coats told ABC.
It was not clear whether Tsarnaev was shot by police or wounded himself.
In the final standoff with police, shots were fired from the boat, but investigators have not determined where the gunfire was aimed, Davis said.
Tsarnaev could be charged any day. The most serious charge available to federal prosecutors would be the use of a weapon of mass destruction to kill people, which carries a possible death sentence. Massachusetts does not have the death penalty.
U.S. officials said an elite interrogation team would question Tsarnaev, a college student, without reading him his Miranda rights, which guarantees the right to remain silent and the right to an attorney. Such an exception is allowed on a limited basis when the public may be in immediate danger, such as instances in which bombs are planted and ready to go off.
The federal public defender's office in Massachusetts said it has agreed to represent Tsarnaev once he is charged.
In an interview with The Associated Press, the parents of Tamerlan Tsarnaev insisted Sunday that he came to the southern Russian regions of Dagestan and Chechnya from January to July last year to visit relatives and had nothing to do with the Islamic militants operating in the volatile region. His father said his son slept much of the time.
When the two suspects were identified, the FBI said it reviewed its records and found that in early 2011, a foreign government — which law enforcement officials confirmed was Russia — had asked for information about Tamerlan Tsarnaev. The FBI said it was told that Tsarnaev was a "follower of radical Islam" and was preparing to travel to this foreign country to join unspecified underground groups.
The FBI said that it responded by interviewing Tsarnaev and family members but found no terrorism activity.
No evidence has emerged since to link Tsarnaev to militant groups in Russia's Caucasus. The Caucasus Emirate, which Russia and the U.S. consider a terrorist organization, on Sunday denied involvement in the Boston attack.
Chechnya has been the scene of two wars between Russian forces and separatists since 1994. That spawned an Islamic insurgency that has spread throughout Russia's Caucasus, with the worst of the violence now in Dagestan.
Despite the violence, Anzor Tsarnaev said Sunday that his son did not want to leave and had thoughts on how he could go into business. But the father said he encouraged him to go back to the United States and try to get citizenship.
In interviews with officials and those who knew the Tsarnaevs, a picture has emerged of the older brother as someone embittered toward the U.S., increasingly vehement in his Muslim faith and influential over his younger brother.
The federal Bureau of Alcohol, Tobacco, Firearms and Explosives was tracing the suspects' weapons to try to determine how they were obtained. Neither of the brothers had permission to carry a gun.
Also Sunday, Boston churches opened their doors to remember the dead and ease the grief of the living.
Boston's historic Trinity Church could not host services Sunday because it was within the crime scene, but the congregation was invited to worship at the Temple Israel synagogue instead.
"So where is God when the terrorists do their work?" Trinity's Rev. Samuel T. Lloyd III asked. "God is there, holding us and sustaining us. God is in the pain the victims are suffering, and the healing that will go on. God is with us as we try still to build a just world, a world where there will not be terrorists doing their terrible damage."
Massachusetts Gov. Deval Patrick asked residents to observe a moment of silence Monday at the time the first of two bombs exploded. The one-minute tribute is scheduled for 2:50 p.m., exactly a week after the attacks.
In New York, thousands of runners donned "I Run for Boston" bibs during a short run in Central Park, one of a number of races held around the world in support of the bombing victims.
Thousands of London Marathon runners offered their own tributes. Sunday's race began after a moment of silence, and many competitors wore black armbands as a sign of solidarity.