13-year-old niece watched her uncle fall to his death on her birthday as a dozen coasters are shut across the US

Hassan Jihad Ibn Kariem, 42, had lost consciousness before his restraint latch came loose on the Goliath hypercoaster at Six Flags Over Georgia on Monday, his niece told her father Joshua Nelson in a panic phone call moments after the fall. The technology teacher at Wesley International Academy in Atlanta was flung from the 70mph ride, striking other riders before landing beneath the attraction, killing him and injuring four children. His wife Eboni was waiting outside and heard authorities announce a fatality, immediately fearing the worst.

The niece had chosen Six Flags as the venue for her 13th birthday that day and was left not knowing what had happened to her uncle after he fell.

At least 12 roller coasters have now been suspended across the US and Canada, including rides at SeaWorld Orlando and La Ronde in Montreal, with ten sharing the same manufacturer and restraint system as the Goliath.

Investigators have revealed that riders on the Goliath had flagged concerns about its restraints before Monday's fatal incident.