LIKE a carefree teenager, Nick Mitchell spent Saturday morning skateboarding and hanging out with his younger brother. Life was good for the Central Coast boy.

Ten hours later the academically gifted teen was dead after a nightmare chain of events sparked by taking an illegal and dangerous drug.

Nick, 15, died after he and a mate experimented with a substance police believe to be LSD.

The drug caused respiratory problems and heart complications for Nick, who could not be revived after his 11-year-old brother found him unconscious in his bedroom.

It had a different effect on his friend, also 15, who, in a psychotic state, ran naked into traffic on a busy road and was hit by a car, leaving him with serious injuries. He is in hospital.

Nick's parents Matthew and Sharon were yesterday struggling with the shock of their son's tragic death and how the popular teen came to be in possession of such a deadly substance.

The two mates had been hanging out together in Nick's granny flat-style bedroom, at the rear of the family's waterfront home in Tascott.

It was during the heatwave on Saturday, and neighbours said they saw the pair wander between the flat and a backyard pool, looking happy and giving no hint of the tragedy which was about to unfold.

About 8.30pm Mrs Mitchell received a frantic call at work from her youngest son to say Nick was not breathing. He'd found his brother slumped on the floor of the bedroom, which police later discovered had been "smashed up".

A neighbour raced over to help and performed CPR on the dying boy, while he waited for paramedics.

In a cruel twist, paramedics racing to the Mitchells' home came across an accident just around the corner where Nick's friend had been hit by a car.

A second ambulance got to Nick and rushed him to Gosford Hospital, where he was pronounced dead.

Head of the NSW Police drug squad Detective Superintendent Nick Bingham said the teenager's death was an absolute tragedy and should pose as a stark warning about the dangers of any drugs.

"LSD, if that's what it was, is an insidious drug. It's got a smiley face on it and looks harmless, but it kills," Supt Bingham said.

Paul Dillon from Drug and Alcohol Research and Training Australia warned that LSD, the once fashionable drug of the 1960s, was having a resurgence in popularity because it is cheap, its effects last much longer than ecstasy and it is not detectable by sniffer dogs: "Some people think LSD went out with the hippie era and isn't around any more, which couldn't be further from the truth."

Nick's death follows that of Brazilian student Roberto Laudisio Curti, who took LSD on the night he was tasered and died during a police chase through Sydney in March.

Detectives fear there could be a toxic batch of the drug circulating, after numerous other incidents were reported where people had suffered serious side effects. Police are awaiting toxicology results, but said evidence found in the boy's bedroom suggested it was likely LSD had been consumed.

Friends of Nick said he was a "smart and popular" boy who had formed a skateboarding club in the Gosford area where teenagers could hang out and share their love of the sport.

On Facebook they lamented a life cut so tragically short.

"Can't believe someone so smart, young and talented could be taken away," Nathan James wrote.

At Gosford High, where Nick was a Year 9 student, counselling was offered to his classmates who were struggling to deal with the senseless death. A private funeral service for Nick will be held next week.