Two explosions at the finish line of the Boston Marathon have resulted in three deaths and more than 170 injuries. The explosions happened more than four hours after the start of the race.Martin Richard of Dorchester, Mass., was waiting for his father at the finish line when the first explosion went off. The 8-year-old boy was running with his mother and sister when the second went off, killing him and injuring his family. Krystle Campbell, a 29-year-old originally from Medford, Mass., was identified as the second victim Tuesday morning. The third victim has not yet been identified.There were 207 Missouri residents, including one from Jefferson City, one from Fulton, one from West Plains and 16 from Columbia, at the Boston Marathon.One Columbia runner was held up at mile 25 because of the explosions. Wilson's Fitness was tracking four Columbia runners, all of whom have confirmed they are OK.Haley Schwarz, Anne Sievers and Clint Smith let their friends and family know they were safe via Facebook. We have also heard that Becky Bond, Jordan Derose, Dana Frese, Shellaine Frazier, Quanna Hafer, Mike Tripp, Laura Hillard, Jennifer Anderson and Dawn Castagno-Dysart are OK.Darrin Young and Dan Heaviland ended up not running in the race, and both are OK.Name City Net Race Time Total Dana Frese(OK) Jefferson City 03:25:44 Jennifer Anderson (OK) Columbia 03:53:59 Becky Bond (OK) Columbia N/A (time at half-way point was 01:56:39) Dawn Castagno-Dysart (OK) Columbia 03:25:03 Jordan Derose (OK) Columbia 03:40:42 Kathy Doisy Columbia N/A (time at half-way point was 02:08:13) Keith Fernandez Columbia 03:18:38 Shellaine Frazier (OK) Columbia 04:11:20 Dan Heaviland (OK) Columbia Did not run Laura Hillard (OK) Columbia 03:07:55 Sean Kennelly Columbia 03:03:52 John Louie Columbia 04:08:18 Haley Schwarz (OK) Columbia 03:40:17 Anne Sievers (OK) Columbia 03:28:27 Michael Tripp (OK) Columbia 03:35:11 William Washington Columbia 04:03:21 Darrin Young (OK) Columbia Did not run Clint Smith (OK) Fulton 03:20:25 Quanna Hafer (OK) West Plains 04:18:07 Joey Frazier (OK) Columbia(hometown) 03:28:38 Jeremy Booker (OK) Poplar Bluff 03:09:37 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.About three hours after the winners crossed the line, there was a loud explosion on the north side of Boylston Street, just before the photo bridge that marks the finish line. Another explosion could be heard a few seconds later. Clint Smith of Fulton finished the race almost an hour before the explosions. He was on the train with his wife and son on their way out of the city when he started getting texts from concerned friends asking if he was okay. At first, he thought they were just checking on him after the marathon, but then he started getting notifications about the explosions.He said it's hard to believe that his family was once standing right where the explosions occurred. "My family stood there, they were standing by those flags...the flags that you (have) probably see on the television...they were right there by that sports store," Smith said. "So when you put it all together and realize what just happened, and if you had just been a few seconds or a few minutes slower it could have been your own family. It just puts everything in perspective and it's just a tragedy."Smith added that crossing the finish line should be one of a person's greatest moments, and as soon as he heard the news, he just prayed for the families.Columbia's Haley Schwarz was in her hotel after finishing the race. A fellow runner was closer and described it as being like the sound of the cannon at an MU football game. Schwarz said she could hear sirens from her hotel window."There are many police and swat teams around our hotel and in the area," she said. "Some hotels are on lock down close to the finish. We are happy to be safe and together at our hotel. We're looking forward to returning to our families!"Jefferson City's Dana Frese finished his fourth Boston Marathon an hour before the explosion. He said he heard "two very loud explosions" from his hotel room, which was one-tenth of a mile from the finish line. His family left the hotel immediately, but have since returned and have been told they will not be able to leave the building tonight. Frese said the whole area is being treated as a crime scene."There are police walking the halls with machine guns and dogs," Frese said. Columbia's Shelly Frazier was not happy with her run, but finished five minutes before the explosion. "I had crossed the finish line, continued on past as we are supposed to do, was getting my medal, warming blanket, water and food, and about five minutes later I saw and heard an explosion back near the finish line," Frazier said. "Most everyone, including me thought it was either a 'celebratory' thing, or at worst an accident."Then she heard the second bomb go off and described the scene as chaos. Frazier is also on lock-down at her hotel. While she didn't know what was happening until seeing the local news reports, she said anxiety was "sky high."Frazier said everyone she traveled with from Columbia is fine, but she is terribly saddened for those injured and killed."This turned what was supposed to be the day of many peoples lives - into the worst," she said. "An unbelievable attack and tragedy."Like many in Boston Monday night, Anne Sievers had limited cell phone service. She texted that she was back at her hotel after the race, which was about six blocks away, and did not hear the blast. Sievers said she saw law enforcement "everywhere.""They are clearing everything they can," she said. "It is like nothing I have seen or experienced before." A person familiar with the situation told the Associated Press that an 8-year-old-boy was killed in the explosions.Police say three people were killed in the blasts. They provided no details, but someone who spoke to a friend of the family and spoke to the AP on condition of anonymity to protect the family's privacy confirmed that an 8-year-old boy was among the dead.The person said the boy's mother and sister were also injured as they waited for his father to finish the race. President Barack Obama, responding to the explosions at the Boston Marathon, says the United States does not know "who did this or why" but vowed that whoever is responsible "will feel the full weight of justice." He said: "We will find out who did this and we will hold them accountable."Click here to access interviews and video of our Boston Marathon coverage.