Early Sunday morning, a truck crashed into a guardrail on a small bridge on I-10, between New Orleans and Baton Rouge. The rail kept the truck from plunging into the swamp below, and only minor injuries were sustained.

But the scene turned to disaster 40 minutes later, when a party bus filled with construction workers heading to help the rebuilding efforts in Baton Rouge smashed into the accident scene, killing two — including a local fire chief — and injuring 41 others.

It was driven by Denis Yasmir Amaya Rodriguez, a 37-year-old Honduran national who lived largely unnoticed in the United States as an undocumented immigrant.

On Sunday, he was booked and charged with two counts of negligent homicide, negligent injuring, reckless operation and driving without a license after police say he inadvertently killed two people and injured more than 40 others after he lost control of a bus he was piloting down a Louisiana interstate and subsequently crashed.

The heartbreaking turn of events began early Sunday morning.

A light summer rain covered much of Louisiana in the pitch-black predawn, as it often does in late August. The roads were slick as the sun rose over Lake Pontchartrain.

About 10 minutes after dawn broke — approximately 6:40 a.m. central time — 30-year-old Javontris Lawson was speeding down I-10 in a 2005 Nissan Titan with 37-year-old Bryan Hill sitting passenger.

That stretch of highway is notorious for speeding, which Lawson was doing when he reached a two-lane bridge.

But the asphalt was wet, and authorities said the truck’s tires likely lost traction as a result of the disastrous combination of excess speed and slippery roads, according to a statement by Louisiana State Police.

He lost control of the nearly 12,000 pound pickup truck, which smashed into the short concrete guardrail that protects drivers from plunging into the murky waters of the Maurepas Swamp Wildlife Management Area, a flooded cypress tupelo swamp that fills with water from both Lake Pontchartrain and Lake Maurepas.

After striking the left guardrail, Lawson must have overcorrected, because the truck slid across both lanes of traffic and struck the right guardrail.

Though the concrete cracked, the guardrail held. The truck didn’t crash into the muddy water below.

Police rushed to the scene. The St. John the Baptist Fire Department drove out one of its fire engines to block errant drivers on the two-lane stretch of interstate from colliding with the crashed and immobile truck while authorities tended to the injured.

The driver and passenger only suffered minor injuries.

Meanwhile, about 25 miles south, down in the New Orleans area, Denis Yasmir Amaya Rodriguez had spent the early morning behind the wheel of a 2002 Eldorado National bus.

This particular model, which ABC noted was owned by Kristina’s Transportation LLC/AM Party Bus, was a party bus — the kind a fraternity might rent out for a date night party.

But Rodriguez was headed to no party. Instead, he and the around 40 construction workers on the bus were headed northwest to Baton Rouge to help with rebuilding after last week’s historic flooding robbed the area of thousands of homes.

Rodriguez had been cited on Aug. 5 — not three weeks earlier — for driving without a license after being pulled over on this very interstate, the Advocate reported.

Still, he drove the bus from the New Orleans area, headed toward Baton Rouge, police said. The party bus drove past the Belle Terre Boulevard exit, which leads into LaPlace, La., and reached mile post 203, the site of the earlier wreck, at 7:17 a.m.

That’s when it appears Rodriguez lost control of the bus, though authorities aren’t sure why.

The fire engine was still parked on the two-lane bridge, blocking the crashed pickup truck. Three firefighters — 32-year-old Nicholas Saale, 35-year-old William Mack Beal and the St. John the Baptist Fire Department district chief Spencer Chauvin — stood near a guardrail.

They saw the party bus approaching “at a high rate of speed.”

The bus crashed into the fire engine and bounced off it like a pinball, then smashing into a 2012 Toyota Camry. The force from that crash sent the Camry careening into a 2016 Chevrolet Silverado, which was pulling a flatbed trailer. It also sent the bus lurching toward the crashed pickup truck and the firefighters guarding the scene.

The bus slammed into all three firefighters, sending them flailing over the concrete guardrail and into the swamp below — an estimated 40-foot drop.

Amid that destruction, the bus — and the mess of crumpled cars — finally came to a rest.

What was left, according to photos of the scene, were scraps of metal and glass among other debris. Most haunting were the several pairs of shoes scattered across the asphalt and the chucks of concrete missing from the guardrails.

Chief Chauvin was airlifted to River Parishes Hospital, where he was pronounced dead. Beal was treated and released from River Parishes Hospital, while Saale remained in critical but stable condition at University Medical Center.

The Camry contained four passengers: driver Marcus Tate and passengers Vontravous Kelly, David Jones and Jermaine Starr.

Twenty-one-year-old Starr was pronounced dead on the scene. Tate was rushed to Our Lady of the Lake Hospital, having suffered serious injuries. Kelly and Jones were taken to University Medical Center, where Kelly is in critical condition and Jones is in serious condition.

The Silverado contained five passengers ranging in age from 10 to 50. They were all transported to local hospitals with minor to moderate injuries.

Meanwhile, the 30 to 40 passengers on the bus were also transported to local hospitals with minor to moderate injuries.

Overall, 41 people were taken from the scene with injuries and two died, according to NOLA.com.

Rodriguez, whom the Louisiana State Police referred to as an “illegal alien,” is an undocumented immigrant and does not have a driver’s license nor a license to operate a commercial vehicle. He has been booked into the St. John the Baptist Correctional Center, the Advocate reported. It was unclear early Monday morning if he has a lawyer or has entered a plea.

“This is a very sad day for all first responders in Louisiana,” said Colonel Mike Edmonson, Louisiana State police superintendent, in a statement. “Our thoughts and prayers are with the St. John the Baptist Fire Department.”

Currently, authorities are attempting to determine what caused Rodriguez to lose control of the bus, WDSU reported. Authorities are also attempting to determine who chartered the bus and why, exactly, the construction crew was headed to Baton Rouge.