U.S. President Barack Obama struck a harsher tone in calling the Boston Marathon bombings a "terrorist act" on Tuesday, removing any doubt that the twin blasts comprise the worst terrorist attack on American soil since Sept. 11, 2001.
As details emerged about the victims and the bombs that killed three people and wounded more than 175 others, the mystery around who is responsible remained.
The FBI agent in charge of the investigation told reporters Tuesday there have been no arrests and "the range of suspects and motives remains wide open."
Special Agent Rick DesLauriers said the two explosions – spaced 10 seconds and roughly 100 metres apart near the race's finish line – erupted around 2:50 p.m. from two black nylon backpacks.
They most likely contained a crude device favoured by terrorist groups in distant war zones: kitchen-variety pressure cookers stuffed with explosives and metal pellets, nails and other deadly shrapnel.
The work of identifying those killed by that explosive combination was nearly complete late Tuesday, when Boston University and the Chinese consulate in New York confirmed that one of the victims is a Chinese grad student who was studying at the institution, located very near the blast zone.
On Wednesday, a state-run Chinese newspaper said the third victim was Lu Lingzi, originally from China's northeastern city of Shenyang.The Shenyang Evening News said that Ms. Lu's father confirmed his daughter's death when reporters visited the family home.
The other confirmed dead are eight-year-old Martin Richard and 29-year-old Krystle Campbell.
The youngest victim was standing with his family when the blast hit. His mother and younger sister suffered serious injuries.
Initially, Ms. Campbell's mother was told she had been injured and taken to hospital. Upon entering the hospital room, she saw only their daughter's friend Karen Rand.
"I said, 'That's not my daughter, that's Karen! Where's my daughter?' " Ms. Campbell told local news channel WCVB. She got her answer when medical staff showed her a picture of one of the three dead spectators. Identification belonging to the friends had been mixed up in the commotion.
Mr. Obama will try to soothe the grief palpable throughout Boston when he speaks at an interfaith service on Thursday.
But on Tuesday, he chose harsher words. "Any time bombs are used to target innocent civilians, it is an act of terror," the President said, calling the attacks a "heinous and cowardly act."
He also attempted to quell wild speculation around the perpetrator, stressing that it remains unknown whether the attacker is foreign or domestic.
Mr. Obama will find a grieving, resilient city upon his arrival in Boston. The crime scene encompassed 12 blocks on Tuesday, cut off by barricades and guarded by armed officers.
On Newbury Street, a shopping destination home to several streets of boutiques, nearly all the stores were shut down at the start of the day. By afternoon, however, more began to open their doors.
Marathoners walked the relatively quiet streets in their distinctive blue-and-yellow jackets. Many had just experienced the highlight of their athletic lives, only to see it followed by a frightening experience they never imagined.
James Hill, the owner of a kitchen-supply store a block from the bombing, said that he usually does brisk business the day after the race. Full of intensity before the competition, the runners wind down the day after, he said, shopping and enjoying the city as tourists. Not so this time, Mr. Hill said.
Many in Boston simply tried to get on with normal routines, partly as a sign of defiance. John Ferrari, 55, a technology consultant, arrived in Boston on Sunday from Colorado for a week-long business trip. Both his hotel and his client's office overlook the site of the bombings. He said the event didn't change his plans.
"You can't bury your head," Mr. Ferrari said. "You can't hide. If you do, they win."
With a file from The Associated Press