A man who shot dead another at a holiday park died of a cocaine overdose while in prison, it has been revealed.

Gunman Jonathon Lawlor was found dead in his cell at HMP Elmley on Sheppey as he awaited trial over the murder of Sam Petrou.

The killer died on October 19 last year, but the cause of his death was only disclosed in an inquest report released on Friday.

The 42-year-old had been on remand after shooting Mr Petrou twice at Eastchurch Holiday Centre in Fourth Avenue, Eastchurch, last June.

He was identified as the man responsible from CCTV, and was later seen fleeing Sheppey in a Jeep owned by his girlfriend Daisy Donohoe, who was in the passenger seat.

Mum-of-two Ms Donohoe was later charged with perverting the course of justice – accused of helping the gunman lie low – but was cleared at a trial at Maidstone Crown Court in March.

She told a jury she’d had a threesome with Lawlor and Petrou 13 months before the 35-year-old dad was gunned down in a friend's caravan at the Cliff Cottage Chalet Park.

While the converted blank-firing self-loading pistol used to shoot Petrou was not recovered, DNA on the bullet casings found at the scene matched Lawlor's.

He was due to face trial at Maidstone Crown Court in December after being arrested in Newcastle five days after the killing.

He had failed to appear in court from prison at an earlier hearing after saying he felt unwell.

The inquest heard that on the morning of his death, he was seen a number of times but did not leave his cell as he complained of a headache and did not want to attend healthcare.

Just before 11.30am, a prison officer attended his single-inmate cell in block house four to begin lunch procedures.

It was at this point Lawlor was discovered lying face down on the floor and unresponsive.

His head and shoulders were underneath the metal frame of his bed, with the rest of his body lying diagonally across the room.

He had a small superficial injury to the right side of his head.

The officer immediately declared an emergency and started CPR.

Other officers attended to help and within 10 minutes a prison doctor arrived and began treatment, which included the use of a defibrillator.

But at 11.47am, Lawlor was declared dead.

A post-mortem examination revealed he had died from cocaine toxicity caused by an excessive use of the Class A drug.

It was also found Lawlor had suffered acute multi-organ failure and pulmonary congestion, which caused respiratory failure and oedema where fluid builds up in the body's tissues, causing swelling.

Lawlor had used drugs outside prison walls but was never observed by staff to be under the influence of substances.

Catherine Wood, the coroner, said in her report she had concerns about the level of staffing at HMP Elmley.

This was because Lawlor had two key work sessions during his four months on remand at the prison when he should have had at least one a week.

The lack of sessions was put down to staff shortages, a high turnover of inmates and the prison being busy.

While this played no part in his death, the coroner said key working sessions can reduce the risk for other prisoners and that the prison has the “power” to take action.

The HM Prison and Probation Service have until Tuesday, January 17, to reply to the report.