After explosives killed three people and wounded about 180 others during the Boston Marathon, details continue to trickle in as investigators sort through evidence.
-- Obama declared an emergency in Massachusetts and ordered federal aid to supplement state and local response efforts.
Details on the bombs
-- Investigators say the dual bombs, which exploded 12 seconds apart Monday, were designed to deliver vicious suffering.
-- One was housed in a pressure cooker hidden inside a backpack, the FBI said. The device also had fragments that may have included nails, BBs and ball bearings, the agency said.
-- The second bomb was in a metal container, but it was unclear whether it was in a pressure cooker as well, the FBI said.
-- Photos obtained by CNN show the remains of a pressure cooker found at the scene, along with a shredded black backpack and what appear to be metal pellets or ball bearings.
-- They were sent to the FBI's national laboratory in Virginia, where technicians will try to reconstruct the devices.
-- In the past, the U.S. government has warned federal agencies that terrorists could turn pressure cookers into bombs by packing them with explosives and shrapnel, and detonating them with blasting caps.
-- Authorities sifted through thousands of pieces of evidence and a mass of digital photos and video clips. They have pleaded for the public's help in providing additional leads and images.
The blasts left three people dead.
-- Martin Richard, an 8-year-old boy with a gap-tooth grin and bright eyes. He loved to run and play in his yard.
-- Krystle Campbell, a 29-year-old freckle-faced woman described as having "a heart of gold."
-- The third victim was Lingzu Lu, a graduate student at Boston University, who had moved to the city last fall, making friends and soaking up new experiences.
-- Of the approximately 178 people injured, 66 remain in area hospitals, according to the latest CNN tally. Thirteen of those are still in critical condition, hospital officials said.
- Martin's mother and sister are among the wounded. His mother underwent surgery for a brain injury, and his 6-year-old sister lost her leg.
-- Doctors say dozens of victims suffered injuries to their legs that involve blood vessels, bone and tissue.
-- The bombings resulted in at least 13 amputations and left doctors picking ball bearings out of victims in the emergency room, a terrorism expert briefed on the investigation said.
-- Dr. George Velmahos, head of trauma care at Massachusetts General Hospital, said his team found "numerous" metal pellets and nails inside patients' bodies. "There are people who have 10, 20, 30, 40 of them in their body, or more," Velmahos said.
-- Dr. Ron Walls also said one patient had more than 12 carpenter-type nails. "There is no question some of these objects were implanted in the device for the purpose of being exploded forward," he said.
Terror group links