In Melbourne, Australia, a series of shark encounters in Sydney have left a man and a boy critically injured, while another boy narrowly escaped harm when his surfboard was bitten. These incidents occurred within just over a day, according to a police announcement on Monday.

Late Monday afternoon, a surfer in his 20s experienced a shark attack at North Steyne Beach, located on Sydney’s Pacific Ocean coastline in the northern suburb of Manly. The attack happened around 6:20 p.m. local time, resulting in severe injuries to his leg, as reported by the police.

Quick-thinking bystanders rushed to the surfer’s aid, pulling him from the ocean before emergency services transported him to a hospital, where he remains in critical condition, authorities confirmed.

The previous day, a 12-year-old boy suffered serious injuries to both legs after leaping from a six-meter (20-foot) ledge known as Jump Rock near Shark Beach, located within Sydney Harbor in Vaucluse. Thanks to the quick response of his three friends, who bravely jumped into the water during the attack to rescue him, the boy was brought safely back to shore.

“The bravery displayed by his friends, who immediately entered the water to save him, is truly commendable,” stated Superintendent Joseph McNulty during a press briefing.

“Those actions of those young men are brave under the circumstances and very confronting injuries for those boys to see,” McNulty added.

News media have reported that the boy lost both legs in the attack.

Around noon on Monday, an 11-year-old boy was on a surfboard that was attacked by a shark at Dee Why Beach, an ocean beach north of Manly. The shark bit off a chunk of the board, but the boy escaped uninjured.

Local authorities said Sydney’s northern beaches, including North Steyne and Dee Why, would remain closed until further notice.

All three beaches near where the attacks occurred have some form of shark protection netting. It was not immediately clear where the attacks occurred in relation to that netting.

Authorities suspect bull sharks are responsible for at least the first two attacks.

Police had warned after the first attack that recent heavy rain over Sydney had increased the amount of fresh and murky water inside the harbor, heightening the bull shark danger.

Dee Why Beach is close to Ocean Reef Beach where a 57-year-old surfer was killed by a suspected white shark last September.

In November, a 25-year-old Swiss tourist was killed and her partner was seriously injured trying to save her as they swam off a national park north of Sydney.