The long yellow school bus comes into the video frame on the right, slowly making its way down the ramp to I-80 west from Route 206.

The driver passes the end of a concrete strip separating the ramp from the interstate. To the left, a dump truck travels down the center lane of the three-lane interstate.

It should be a simple merge for the bus after the solid lines of the ramp lane turn dotted, a smooth entrance onto the relatively empty highway.

But without warning, the driver makes a seemingly inexplicable sharp left onto the interstate, darting nearly perpendicularly across the highway.

The driver, a source says, is heading toward a cut-through to the eastbound lanes, the kind used by State Troopers and other emergency vehicles, but occasionally repurposed by motorists making illegal u-turns.

The dump truck swerves to try to avoid the collision, but it's simply not possible. The bus is too long and takes up too much of the highway for a fully loaded dump truck to completely avoid.

NJ Advance Media was allowed to view the DOT video by a person who has a digital copy in their possession. The person's phone was small and the actual crash occurred in the distance of the west-facing camera's point of view high above the roadway, so the view is not in high-definition.

The violent collision separated the bus from its chassis, killing a 10-year-old girl and a 51-year-old fifth-grade teacher, and seriously injuring dozens of other kids from East Brook Middle School in Paramus.

It thrust the community into deep mourning while also prompting a sense of bewilderment at the chain of events. The most urgent question is why the bus driver was even on that particular Route 206 ramp.

The bus driver's name has not been released, but he was identified Monday by CBS as 77-year-old Paterson resident Hudy Muldrow Sr.

The bus was one of the three taking children to Waterloo Village in Byram, a late-year field trip to a restored canal town.

The two other buses arrived at Waterloo, but it remains unclear how the third bus managed to separate from the convoy and end up back on I-80.

The initial State Police press release on the Thursday crash, sent out that evening, said that "a school bus carrying 38 fifth-grade students and seven accompanying adults from East Brook Middle School entered westbound Interstate 80 from southbound U.S. Highway 206."

But when news outlets, including NJ Advance Media, reported on Friday that sources confirmed the bus was attempting an illegal u-turn, it seemed more likely that the bus had simply missed the exit.

To reach Waterloo Village, the bus should have gotten off I-80 at Route 206 northbound and taken the first exit, simply following the signs to Waterloo.

How the bus became turned around and headed back southbound down Route 206 and onto Route 80 remains a mystery.

A State Police spokesman said Monday that the agency stands by its initial statement, but would have no further comment until an investigation is complete. The Morris County Prosecutor's Office declined comment Monday, citing an active investigation.

Hundreds of mourners gathered Monday to say goodbye to Miranda Vargas, the fifth grader who died in the crash, and Paramus held a town-wide vigil on Sunday night for her, teacher Jennifer Williamson, and the other children and adults hurt in the crash.