Four people were killed and dozens were injured Monday when an Amtrak train derailed after hitting a dump truck that was in an uncontrolled public crossing in Mendon, Missouri, according to Amtrak and officials.
Eight passenger cars and two locomotives derailed at about 12:42 p.m. local time, Amtrak said.
Missouri State Highway Patrol Cpl. Justin Dunn initially said two of the train's passengers were killed, along with someone who was in the dump truck.
On Tuesday, the highway patrol said a third train passenger died overnight, bringing the total number of deaths to four.
At least 150 people involved the crash were treated at 10 hospitals in the area for minor to serious injuries, the National Transportation Safety Board said in a statement, citing updated information from Amtrak and law enforcement.
NTSB investigators said Tuesday that the dump truck was transporting aggregate to contractors nearby for an Army Corps of Engineers project. The NTSB said the vehicle was crossing the track when the backside was hit by the train.
The agency said it was downloading the event recorders from the train and noted the train had two forward-facing cameras. The dump truck also had a data recorder that investigators are trying to examine, according to the NTSB.
"It was something that you never think is going to happen, but when it does happen, it's far worse than anything you could have imagined," Jason Drinkard, a passenger on the train, told ABC affiliate station KMBC in Kansas City, Missouri.
Drinkard, a high school teacher, said he was traveling with his wife and six students to Chicago for a conference, when the crash occurred. He described seeing the "carnage," with injured passengers and crew unable to walk.
The train was en route from Los Angeles to Chicago with 275 passengers and 12 crew members on board at the time of the crash, Amtrak said. All the train occupants from the scene were evacuated, according to Dunn.
Officials at Hendrick Medical Center accepted seven patients from the scene, while officials at MU Health Care University Hospital/Columbia said its facility was treating 16 patients as of 10 p.m. ET Monday. Pershing Memorial Hospital received between 15 and 20 people from the accident.
Passenger Rob Nightingale, 58, told ABC News his train car tipped to the side and he climbed through a window to escape. He said he saw a little girl crying and her family trying to comfort her.
Some people were covered in blood, he added.
Aboard the train were two Boy Scout troops from Appleton, Wisconsin, that sprang into action, breaking windows and helping to evacuate passengers, two of the scouts' mothers told ABC affiliate station WBAY in Green Bay, Wisconsin.
Berken and Tierney said they both described a nerve-racking period of time between learning of the crash and hearing that their sons survived the crash without injuries.
"Until I heard from my son an hour later, that he was OK, I couldn't stop shaking or crying," Berken said.
Tierney added, "It was a phone call that no parent should ever have to receive. It was probably way up there on the scariest moments of my life."
Scott Armstrong, a spokesman for the Boy Scouts of America, told ABC News Tuesday that there were 16 scouts, ages 14 to 17, and eight adult chaperones who were returning home from a week-long backpacking trip at a wilderness camp in New Mexico. He said three of the adult chaperones suffered non-life-threatening injuries and remained in the hospital in stable condition.
Armstrong said one of the scouts was treated at a hospital for minor injuries and released.
"Our scouts immediately sprung into action and assisted other people in getting out of the train wreckage," Armstrong said. "The train itself is physically on its side, which can be very traumatic and disorienting, and (the scouts) helped a lot of people with basic first aid and made sure they got the proper medical attention once it arrived on scene."
He said most of the scouts on the trip had achieved their first aid merit badge and some had been awarded their emergency preparedness merit badge.
"Frankly, we know what these kids are capable of," Armstrong said. "I've always described that scouting takes ordinary kids and enables them to do extraordinary things and that was on full display yesterday."
Armstrong said one of the scouts, a 15-year-old he described as a troop senior patrol leader, went to the front of the train and discovered the driver of the dump truck that was hit, who had been ejected from his vehicle and landed in field adjacent to the toppled train. He said the scout attempted first aid on the dump truck driver and summoned state police and emergency responders, who continued to try to save the man's life.
"They continued to give aid and then wound up just giving comfort, frankly, as he passed away on the scene, unfortunately," Armstrong said.
He said the scouts will be monitored in the coming weeks to ensure they are both mentally and physically OK.
"It's a pretty traumatic experience," Armstrong said. "It's not always evident immediately after any incident like this and so we have mental health professionals that we're in consultation with to make sure that those services are available to the scouts and the leaders as necessary."
MORE: 3 dead, 2 injured after Amtrak train collides with car in California: OfficialsMissouri Public Safety officials, highway patrol troopers and other personnel were dispatched to the scene, Missouri Gov. Mike Parson tweeted.
Mendon is about 100 miles northeast of Kansas City, Missouri.
The NTSB also said there are 130,000 passive crossings in America right now, which account for about half of all crossings. The agency said it has made recommendations for years about transforming and improving “passive” crossings.
It would’ve cost $400,000 to add cross arms, lights, and bells to the Mendon crossing, according to the NTSB.
The crash came a day after an Amtrak train collided with a car in California, killing three people.
U.S. Transportation Secretary Pete Buttigieg said in a statement, "My thoughts are with the victims and families affected by today's Missouri train derailment and the Northern California collision that occurred over the weekend. I have been updated on these crashes and my team is in communication with Amtrak and the relevant authorities."
Federal Railroad Administration personnel are en route to Mendon, where they will support NTSB investigators, Buttigieg added.
ABC News' Sam Sweeney, Gio Benitez and Bill Hutchinson contributed to this report.