WATCH: A missing teen is found alive after 6 days in the Australian woodlands

A 17-year-old boy with autism was found alive Thursday after six days lost in eastern Australian woodlands.

The boy, whom police identified only as William, had begun camping with a teenage friend when he disappeared last Friday near Walhalla, a former gold-mining town 185 kilometers (115 miles) east of Melbourne, police said.

A police helicopter crew found him surrounded by wilderness lying asleep on a flat rock beside a creek, and he was later reunited with his mother. William was in good spirits and mostly in good health, the police statement said.

Video shot from the rescue helicopter showed he was shirtless and sunburned. He was wearing shorts and boots and was using towels as blankets.

“I’m just over the moon that he’s alive,” his mother, Elizabeth, told reporters. The AP has decided not to provide her family name to avoid identifying her son.

“And he’s never leaving the house again. He’s grounded for life. He’s not going anywhere ever again,” she joked.

William was later taken to a hospital for his health to be monitored, police said.

William’s family have said he has Level 2 autism. That requires “substantial support,” according to the Australian advocacy group Autism360.

Such a person may have marked deficits in verbal and non-verbal social communication and rely heavily on routines and predictable activities. Disruption can cause significant distress.

The Southern Hemisphere spring weather had been mild for the past week in the alpine region where William was lost and there had been little rain.

Elizabeth had dropped off her son and his friend last Friday for a weekend of camping. William walked a short distance from the campsite to the drop-off location to collect more camping equipment but never returned to his friend, police said.

After becoming lost, William trekked for days up and down “some very steep terrain,” Acting Police Inspector Jason Benbow said.

He spent the last two days where he was found at the creek, trapped by the steepness of his surrounds 2 kilometers (1.2 miles) from the his camp site, Benbow said.

“He woke up to the sound of the helicopter, gave them a thumbs up and they winched him to safety,” Benbow told reporters.

The extensive police search for him involved more than 100 emergency services personnel and volunteers.