Mayhem descended on the Boston marathon Monday afternoon, when an explosion at the finish line killed at least three and injured more than 130. Here's an account of the first six hours of breaking news from the scene in downtown Boston.

John Tlumacki / Boston Globe / Getty Images Police officers draw their weapons after hearing a second explosion near the finish line of the 117th Boston Marathon on April 15, 2013. See more photos from the scene here.

Mayhem descended on the Boston marathon Monday afternoon, when two explosions at the finish line killed at least three and injured more than 130. What follows below is an account of the first six hours of breaking news from the scene in downtown Boston. TIME is no longer updating this page regularly, but keep visiting TIME.com for the latest dispatches and analyses about the event.

9:00 p.m.: During a press conference with the Boston Police Department, Commissioner Edward Davis confirmed that there are now at least three dead, but denied reports that there is a suspect in custody. FBI’s Richard DesLauriers said that the agency is taking over the investigation of the Boston marathon explosions, calling it a “potential terrorist investigation.”

Massachusetts Governor Deval Patrick (D) said the city of Boston will be open tomorrow, but “it will not be business as usual.” There will be a “heightened law enforcement presence.” There will be random checks of backpacks and parcels on the T.

8:45 p.m.: From a statement published on Facebook by former Massachusetts Senator Scott Brown (R): “Like many of you, I was at first horrified. Now I am mad. This was a cowardly act, just cowardly. Our country is at its best when our back is against the wall.”

8:35 p.m.: The NBA has canceled Tuesday’s Boston Celtics and the Indiana Pacers game in Boston, New York Times’ Howard Beck reports.

8:31 p.m.: Hospitals are now reporting that at least 134 people have been injured — and “at least 15 critically,” per the Associated Press.

8:04 p.m.: According to the latest information from the Associated Press, at least 124 people sustained injuries in today’s explosions — ranging from cuts and bruises to amputations. Of those injured, at least 15 are in critical condition.

7:57 p.m.: The FBI has released a statement, saying that federal agents are on-scene assisting the Boston Police Department with their investigation: “The situation remains fluid and it remains too early to establish the cause and motivation.”

7:40 p.m.: TIME’s Jay Newton-Small is on-scene in Boston, and posted this picture of the marathon clock still ticking:

The Boston marathon clock is still running under the Citgo sign. 9h30 pic.twitter.com/ADaa1n1mEJ — Jay Newton-Small (@JNSmall) April 15, 2013

7:35 p.m.: Thanks to donations, the Red Cross reports that it has enough blood to help the victims.

7:26 p.m.: The Boston Globe confirms reports that one of the deceased is an 8-year-old child.

Boston Globe confirms that one of two victims killed in Marathon explosion was an 8 year old boy. http://t.co/21aH33D6st — The Boston Globe (@BostonGlobe) April 15, 2013

6:56 p.m.: Speaker John Boehner has asked for all flags around the U.S. Capitol to be lowered to half-staff Tuesday out of respect for the incident. The injury toll has now been raised to more than 100. CNN is reporting that Sen. Dianne Feinstein, chairman of the Senate Select Committee on Intelligence, said this evening they had no intelligence on this before the attack.

6:36 p.m.: While President Obama did not use the word “terror” in his address this evening, a White House official tells TIME’s Zeke J. Miller that they are investigating it as an “act of terror.”

“Any event with multiple explosive devices — as this appears to be — is clearly an act of terror, and will be approached as an act of terror. However, we don’t yet know who carried out this attack, and a thorough investigation will have to determine whether it was planned and carried out by a terrorist group, foreign or domestic.”

6:32 p.m.: According to Runner’s World magazine, the Boston Athletic Association said 17,584 runners out of 23,326 total had crossed the finished line at the time of the blast. The last recorded finish time was 2:57 p.m.

The American Red Cross is helping to connect victims with their families and coordinate volunteer efforts in the affected areas. The organization has set up a Safe and Well website where people can update family and friends with their current status and whereabouts. Blood donations are also being accepted throughout Massachusetts. Click here to find out more.

6:26 p.m.: According to CNN, citing a spokeswoman, Children’s Memorial Hospital in Boston has admitted seven injured people from the blast, six of them children.

The fire incident at the JFK Library has been mitigated, the library is reporting.

The fire in the building is out. Appears to have started in mechanical room. All staff and visitors are safe & accounted for. — JFK Library (@JFKLibrary) April 15, 2013

6:14 p.m.: In a short 3-minute statement just after 6 p.m. Monday, President Obama reflected on the horror of today’s situation. “On days like today there are no Republicans and Democrats — we are Americans united in our concern for our fellow citizens.” Obama highlighted the uncertainty of the situation: “We still do not know who did this or why, and people shouldn’t jump to conclusions before we have all the facts.” But the president affirmed that the U.S. is gathering as much information as possible. “But make no mistake we will get to the bottom of this. And we will find out who did this. We will find out why they did this. Any responsible individuals — and responsible groups — will feel the full weight of justice… We will find out who did this and we will hold them accountable.” The president did not call the incident a terror attack, however. Read the full transcript.

6:04 p.m.: Commissioner Ed Davis noted in a press conference that the JFK Library fire was a result of “an incendiary device or a fire” and was not related to the marathon blasts.

He underscored that despite some conflicting reports, no suspect is in custody yet, but they are questioning certain individuals. No one has claimed responsibility for the attack. More than 100 are being treated for injuries.

5:45 p.m.: A government official tells TIME the explosions in downtown Boston were the result of crudely made devices.

President Obama is slated to give a White House briefing at 6:10 p.m.

5:43 p.m.: While an earlier intelligence briefing indicated that cell phone service had been shut down in the Boston area, two national carriers refuted this. Officials with Verizon Wireless and Sprint Nextel said there have been no requests to shut down cell phone services, which are still operating under heavy traffic in Boston, the AP reports. Sprint spokeswoman Crystal Davis said: “Minus some mild call blocking on our Boston network due to increased traffic, our service is operating normally.”

5:31 p.m.: The third blast at the JFK Library was apparently “fire related,” according to Boston Police Department spokeswoman Cheryl Fiandaca.

5:26 p.m.: The White House has released a photo of President Obama on the phone with FBI Director Robert Mueller, receiving an update on the situation. Flanking the president are Lisa Monaco, Assistant to the President for Homeland Security and Counterterrorism, and Chief of Staff Denis McDonough. (This photo was originally posted to Flickr and taken by White House photographer Pete Souza.)

5:11 p.m.: A law enforcement official tells the Associated Press that cell phone service has been shut down in the Boston area to prevent any potential remote detonations of explosives. Given the inability to reach runners and loved ones, Google has launched a Person Finder for anyone with information about people who may have been involved in the blast.

Over the years, the Boston Marathon has undergone numerous security overhauls. TIME writer Katy Steinmetz reports: Under heightened security in 2002, 600 police officers joined the runners. There were also an unprecedented 1,500 state and local police patrolling the route and another 1,500 security guards. There were 415 National Guard troops on hand. Helicopters, bomb-sniffing dogs, hazmat teams and radiation detectors were added. Boston Globe compared to security used for the Olympics and Super Bowl. According to the Mass. National Guard website, more than 400 troops were involved in 2013, too. From the release: Pfc. Matthew S. Knowlton, a military policeman with the 747 Military Police Company, was one Soldier assigned to help out at the starting line. Describing the scene Knowlton said, “This is a very positive setting, I’m just happy to be here. There are a lot of people here but it’s a great crowd.”

5:08 p.m.: Video from overhead the finish line shows the terror in the wake of the blasts.

4:50 p.m.: In a Monday evening press conference, Boston Police Commissioner Edward Davis discussed the incident: “At 2:50 p.m. simultaneous explosions occurred” near the finish line, about 75 to 100 yards apart. “Each scene resulted in multiple casualties” but wouldn’t confirm the exact number. As fearful spectators ran from the scene, a number of bags were left behind; the Boston Police Department is treating all left-behind bags as a “suspicious device.”

Davis confirmed a third explosion at the nearby JFK Library, possibly unrelated, but stated that as of now they have not found another explosive device. The JFK Library is located 5 miles southeast of the blast site near Copley Square.

4:47 p.m.: Other cities across the world are now reevaluating their marathon security plans. According to the Associated Press, police departments in New York City, Los Angeles, London and other cities are stepping up security efforts following the explosion while British police are reviewing security plans for the London Marathon, scheduled for next Sunday.

4:42 p.m.: Statement from Massachusetts Governor Deval Patrick: “This is a horrific day in Boston. My thoughts and prayers are with those who have been injured. I have been in touch with the President, Mayor Menino and our public safety leaders. Our focus is on making sure that the area around Copley Square is safe and secured. I am asking everyone to stay away from Copley Square and let the first responders do their jobs.”

4:40 p.m.: The New York Times has unveiled a map of the explosion site in proximity to the finish line.

https://twitter.com/digg/status/323892943767339009/

4:27 p.m.: According to intelligence officials, two more explosive devices were found at the scene near the marathon’s finish line and are currently being dismantled.

4:24 p.m.: The White House says President Obama is tracking the situation closely. From TIME correspondent Zeke J. Miller in Washington, D.C.: “Shortly after being notified of the incident around 3pm EDT, the President received a briefing from Homeland Security adviser Lisa Monaco and other members of his senior White House staff in the Oval Office. The President called Boston Mayor Tom Menino and Massachusetts Governor Deval Patrick to express his concern for those who were injured and to make clear that his administration is ready to provide needed support as they respond to the incident.”

4:08 p.m.: Roughly three hours after the winners crossed the finish line, there was reportedly a loud explosion on the north side of Boylston Street, just before the photo bridge that marks the finish line. Another explosion was heard by spectators a few seconds later. Initial reports from the said at least two people were dead, and 23 injured. (Watch here for further updates.)

Boston marathon organizers said in a statement on Facebook that the explosion was caused by two bombs: “We are working with law enforcement to understand what exactly has happened.”

Bloody spectators were being carried Monday to the medical tent that had been set up to care for fatigued runners. Police wove through competitors as they ran back toward the course. “There are a lot of people down,” said one man, whose bib No. 17528 identified him as Frank Deruyter of North Carolina. He was not injured, but marathon workers were carrying one woman, who did not appear to be a runner, to the medical area as blood gushed from her leg. A Boston police officer was wheeled from the course with a leg injury that was bleeding.

3:45 p.m.: A White House official told TIME that President Obama had been notified of the incident and that the administration was in contact with local authorities. Airspace above Boston was closed late Monday afternoon. Pedestrians were restricted from the sidewalk in front of the White House, as police cordoned off the area with yellow tape.

“There are people who are really, really bloody,” said Runner Laura McLean of Toronto, who reported hearing two explosions outside the medical tent. “They were pulling them into the medical tent.”

Cherie Falgoust was waiting for her husband, who was running the race: “I was expecting my husband any minute,” she said. “I don’t know what this building is … it just blew. Just a big bomb, a loud boom, and then glass everywhere. Something hit my head. I don’t know what it was. I just ducked.”

After September 11th, the Federal Bureau of Investigation started adding more protection to the race as part of increased counterterrorism efforts, director Robert S. Mueller, III said in a 2002 speech.

Most people learned the news from Twitter, as numerous tweets included photos of a chaotic scene at the finish line:

[tweet https://twitter.com/JoshCox/status/323871112805101568/photo/1%5D

[tweet https://twitter.com/BostonGlobe/status/323873235949207552%5D

[tweet https://twitter.com/nycjim/status/323874327583932416%5D

[tweet https://twitter.com/stevesilberman/status/323880924016168961%5D

CBS’s Boston affiliate WBZ captured the moment the explosion occurred on camera:

[youtube=http://www.youtube.com/watch?v=rfCK3Ar7Yus&feature=youtu.be]

The windows of a Starbucks coffee were blown out in photo taken by user stackiii:

– The Associated Press contributed to this report