Shane William Ryan claimed his unprovoked act of violence inside a Darwin gym was an accident.

The CCTV footage told a very different story.

Ryan and another gym user were alone inside the Next Level Gym in Rosebery, a suburb just outside Darwin.

The other gym user was performing a bench press — lifting two dumbbells while lying flat on his back on a bench.

In footage shared by the NT Supreme Court, Ryan could be seen picking up a 20kg weight, walked towards the other gym user and dropping the weight directly on his face.

The victim began bleeding immediately from his head where he would later be diagnosed with a fractured skull.

Ryan, feigning an ankle injury, walked away from the victim before returning with a phone to call an ambulance.

For months, the 33-year-old claimed it was an accident. But in the Supreme Court last month he changed his story.

The CCTV footage has only recently been made public.

Ryan was jailed for 19 months for an act that Justice John Burns said was “an extremely dangerous act” on a person “unable to protect himself”.