OAKLAND, Ia. — Megan Klindt, 16, left her house to board the school bus shortly before 7 a.m. Tuesday, the only student aboard as Donald Hendricks began to back the bus out of the driveway in rural Pottawattamie County.

But something went terribly wrong. The bus ended up in the ditch and caught fire.

Klindt's family saw from the house and called for help, saying that the people on the bus couldn't escape. At about 7:02 a.m. Tuesday, dispatchers scrambled volunteer firefighters, medics and full-time sheriff's deputies to rush to the Klindt home. The 911 caller said the bus was engulfed in flames.

At 7:15, a sheriff's deputy arrived. "Deputy on scene is unable to get inside the bus," a dispatcher said.

By the time the fire was extinguished and first responders could check on them, Klindt and Hendricks were dead.

Authorities said they did not know Tuesday why the fire started or why it burned so intensely. Students at Riverside Junior/Senior High School in Oakland, about eight miles from the Klindts' home, mourned the sudden loss. Hendricks, a 74-year-old city councilman in nearby Carson, was remembered as a man devoted to faith and family.

The National Transportation Safety Board said on Twitter that it was sending a team to investigate the incident.

About 100 people gathered Tuesday night to remember Hendricks and Klindt at Fellowship of Faith Christian Center in Oakland, where parents and children hugged and cried. During the service, Pastor Brody Tubaugh, of Carson United Methodist Church, told mourners he had struggled with what to tell them.

"We come with heavy hearts," Tubaugh said. "And the pain won't just instantly go away."

Hendricks was re-elected in November to a new term on Carson's city council. His grandson, Denton Hendricks, said in an interview that the driver was a supporter of Riverside's sports teams, attending Denton's football games and wrestling matches. He went to Carson United Methodist Church every Sunday and had been married to his wife, Kathleen, for more than 20 years.

“He was one of a kind,” said Denton, 19, of Carson. “He had a deep pride for our community.”

Hendricks grew up in southwest Iowa and moved to Lake Elsinore, California, when he was 15. He moved back to the Carson area and met Kathy in about 1994, Denton said.

He and Kathy would make yearly trips, Denton said, to visit California, Washington, Nevada and Texas. The two, who did not have children together, loved to travel.

“They were like the perfect couple,” he said. “You could just see the love in them.”

Outside the vigil Tuesday night, Kasie Haven, who has three young children in the school district, described her worried reaction to the news: “At first, I prayed to god that my kids weren’t on the bus.”

Rachel Longcor, who has two children who attend Riverside, had the same thought, followed by sadness for the families of those who'd been killed. Klindt had two older sisters and one older brother, Longcor said.

“I can’t imagine what that family is going through,” said Longcor, 35, of Oakland.

Fire 'couldn't have hit us at ... a worse time'

Chief Deputy John Reynolds of the Pottawattamie County Sheriff's Department said the 911 call came right at the end of the 11 p.m. to 7 a.m. shift.

"It couldn't have hit us at probably a worse time. I mean, we were right in the middle of changing shifts," Reynolds said. "When the call came in at 7:02, I think the response time was about as quick as we probably could have gotten there."

AUDIO: Dispatchers respond to fatal Iowa school bus fire

Several of the night cars were still listening to dispatch calls when the fire started, so six deputies were active when the call came in, Reynolds estimated.

At minimum, four deputies patrol Pottawattamie County at all times, Reynolds said. If the sheriff's office has additional staffing, there may also be roving cars and cars working on traffic monitoring.

Pottawattamie County has one full-time fire department out of Council Bluffs, plus 14 volunteer fire departments spread around the county. The nearest ambulance to the scene was in Oakland, Reynolds said.

Reynolds said it was too soon to say why the fire started. He said there was no bad weather in the area.

Carson, Macedonia and Oakland firefighters reported to the scene, along with sheriff's deputies and other emergency responders.

The Riverside school district has more than 600 students, with school buildings in Oakland and Carson. The district includes portions of central and eastern Pottawattamie County.

In a statement on Facebook, Tom Mitchell, the district's superintendent, described the deaths as a tragedy. "Our hearts go out to their families and loved ones," he said.

Mitchell and other administrators could not be reached to comment Tuesday.

It was not clear how long Hendricks had been driving for the district. Online Iowa court records show no citations related to operating a school bus.

This morning, the Riverside Community School District suffered a tragedy when we lost a student and an employee in a school bus accident. Our hearts go out to their families and loved ones. The investigation into the cause of the accident is underway, and we are cooperating with law enforcement as they do their work. The safety of students and staff is the top priority for the District. School is in session and a Crisis Team from the Green Hills Area Education Agency along with area schools counselors and many community volunteers have been deployed to all our buildings to assist students and staff. All after school activities for today have been cancelled and will be rescheduled. Pottawattamie County Sheriff Department is handling the scene and will update the media later today. We will release more information as it becomes available to us.

Check back to the Register for updates to this story.

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