UPDATED: April 16, 2013, at 1:20 p.m.

The final mile of the Boston Marathon was transformed into a grisly and chaotic scene Monday when two bombs exploded near the finish line at around 2:50 p.m., leaving three dead and more than 130 injured. Witnesses described dozens of victims sprawled across the course and limbs left lying amid broken glass on a blood-stained Boylston Street in the Back Bay neighborhood of Boston.

Multiple news outlets reported that among the dead was an eight-year-old boy. Late Monday night, CNN reported that at least 17 people were still in critical condition with injuries from the attack, and that doctors were “pulling ball bearings out of the people in the emergency room.”

Late Monday night, Peter J. Fagenholz, a surgeon at Massachusetts General Hospital, told reporters that he and his colleagues had performed “several amputations” that evening.

Dean Smith, a Marathon attendee, was standing near the finish line waiting for his son to finish the race when the bombs went off. He said he sustained shrapnel injuries in his leg and back, and that six hours after the blasts, his ears were still ringing.

“I was feet away from the second explosion,” said Smith, who has no relation to the Dean of the Faculty of Arts and Sciences at Harvard. “My wife said I flew five feet into the air. It was like something out of a movie, and I saw lots of blood.”

After the attack, Boston Police Commissioner Edward F. Davis recommended that residents stay home and not travel outside in large groups. He also said that each package and bag left along the marathon route was being “treated as a suspicious device.”

The Federal Aviation Administration implemented a no-fly zone around some parts of Boston, and traffic at Logan International Airport was temporarily halted to adjust the airport’s runway configuration.

During a press conference Monday night, Massachusetts Governor Deval L. Patrick ’78 called for Boston residents to “be in a state of heightened vigilance” as the investigation of the attacks continues.

Patrick said that the area surrounding Boylston St. will continue to be “locked down” until the investigation is complete.

“It’s not going to be easy, simple, or regular,” he said of mobility around the cordoned-off section of Boylston St.

Establishments surrounding the site of the explosion—Boston Public Library in Copley Square, The Shops at Prudential Center, the Copley Place mall, and the Hynes Convention Center—remained closed late Monday night.

The Massachusetts Bay Transportation Authority’s green, red, and orange lines was expected to resume activity as usual on Tuesday, with the exception of the Copley Station stop on the Green Line, which was expected to remain out of service.

Richard A. Davey, the state’s secretary of transportation, told the Boston Globe that T patrons could be randomly searched, and that there may be state troopers and members of the National Guard at subway stations. Exit 22 off of the Massachusetts Turnpike, which flows directly into Copley Square, was expected to be closed to traffic.