Experienced surfer Mercury Psillakis, 57, suffered catastrophic injuries and died at the scene after being mauled by a “large” shark about 10am while surfing at Long Reef Beach near Dee Why.

A NSW shark net trial to remove three nets this summer has now been halted, NSW Premier Chris Minns has confirmed.

“We need to understand what happened and how it happened,” Minns told Sky News, after describing the attack as an “awful tragedy”.

“I think it’s also worth reporting that Dee Why is a netted beach and was not going to be part of the trial, so I need to understand whether the shark got inside the nets or how the system’s operating, before we make big moves.”

Documents obtained via freedom of information laws found over 200 sea creatures, including dolphines, turtles and endangered grey nurse sharks, were killed by the nets last summer.

The trial would have seen three beaches across Waverley, Northern Beaches and Central Coast councils have nets removed.

Nets were installed on Monday at 51 beaches between Newcastle and Wollongong.

The NSW government annually installs mesh nets at beaches up and down the coast every summer, along with drumlines, drone surveillance and listening stations as part of a $21.5 million shark safety initiative

Northern Beaches Police Area Commander John Duncan yesterday said the attack was a “freak incident that happens very, very rarely”.

There has not been a fatal shark attack on a netted NSW beach since 1951.

The exact species of shark which attacked Psillakis remains unknown, however a great white was detected by drumlines prior to the incident.

Beaches across Sydney’s northern region remained closed today as members of the Dee Why Surf Life Saving Club patrolled the water and monitored it via drones.

President of the Surf Life Saving – Sydney Northern Beaches Rob McGibbon said Dee Why wold remain closed for up to 72 hours.

The attack took place south of the lagoon at Long Reef, a section of the popular beach which is netted.

“We have to co-exist, and we have the technology,” she said.