Seatbelt was never properly secured around 6-year-old who died on Colorado amusement park ride

GLENWOOD SPRINGS, Colo. -- Colorado investigators now say they know why a 6-year-old girl died riding an amusement park ride on Sept. 5.

Wongel Estifanos was riding the Haunted Mine Drop ride at Glenwood Caverns Adventure Park when she fell to the bottom of the attraction's 110-foot shaft.

"This is a parent's worst nightmare and something you don't wish on your worst enemy," friend of the family Bementayehu Mekonnen told ABC News.

Investigators with Colorado's Amusement Rides and Devices Program determined that Estifanos was not wearing a seatbelt when the ride started, according to a report released Saturday.

READ: Full report into death of Wongel Estifanos

When reviewing surveillance video, investigators determined Estifanos sat on top of the ride's two seatbelts. She was able to sit on top of the ride's latched seatbelts because the seat she boarded was unoccupied on the previous ride cycle.

In addition, the ride operator had not unlatched the seatbelts after the previous ride cycle.

So when Estifanos arrived, she sat down in the seat without the seatbelt secured around her.

This triggered the control system of the ride to sound an alarm, alerting the ride operator that there was a problem.

The ride operator investigated the problem, tugging on the tails of the seatbelts to make sure they were all latched properly. In doing this, the ride operator pulled on Estifanos' seatbelt tail to prove that it was latched into the lock. The ride operator did not notice that the seatbelt was not properly around her lap.

The ride still would not start, so the ride operator called another operator to help.

The assisting ride operator used a manual override to unlock the restraints. This ride operator then removed and reinserted all the seatbelt locks.

They then rechecked Estifanos' seatbelts, making the same error as the first ride operator -- failing to notice that the seatbelt straps were under Estifanos instead of securely across her lap.

However, since the ride had been manually overridden and reset, the ride's control system no longer sounded any alarms and instead allowed the operators to initiate the ride.

The Colorado investigators determined that lack of procedures, inadequate training, multiple ride operators in charge of a single ride cycle and the restraint system itself were all factors in the tragic death of Estifanos.

The Haunted Mine Drop will remain closed until the ride and ride operators address all the factors that led to the tragedy and the state inspectors re-permit its operation.