A grieving mother today recounted the moment her son “karate kicked” a hole in a window during an ecstasy-fuelled breakdown before running to his death in the River Lea.

Hackney Gazette: Tributes at the scene where Jack drowned (Picture: Ellie Hoskins)Tributes at the scene where Jack drowned (Picture: Ellie Hoskins) (Image: Archant)

Anna Susianta said Jack – an A-level student who had just turned 17 - had been “full of the joys of life” before going off to the Secret Garden Party festival in Cambridgeshire on July 23 last year.

But when he returned four days later on Monday, he was “over emotional, couldn’t stop crying”, and his brother and “best friend” Sam realised he was coming down from MDMA - which he admitted having taken a little of every day there.

“I had never seen him like that before,” Mrs Susianta, former head teacher at Rushmore Primary School, told jurors at St Pancras Coroner’s Court this morning, after she broke down in the witness box as she showed them a photograph of her son.

“We tried to look after him and explain he was coming down from drugs, but he didn’t understand what was causing him to be like that,” she continued.

Hackney Gazette: Tributes at the scene where Jack drowned (Picture: Ellie Hoskins)Tributes at the scene where Jack drowned (Picture: Ellie Hoskins) (Image: Archant)

The family lay down together in bed at their home in Thornberry Road to “try and calm him down”, but he was “nervous and agitated” and when he heard a baby crying in the house opposite he didn’t recognise the noise.

His family called the police after he ran off outside and jumped on a bike, and he was found “looking up at the sky by a traffic cone”.

Jack, whose socks were “in holes from running all night”, was taken to Homerton Hospital, and sustained bruises and a swollen lip after police used force to get him inside.

He was told that he wasn’t under arrest, but once inside the ward he was handcuffed with his arms behind his back.

Hackney Gazette: Tributes at the scene where Jack drowned (Picture: Ellie Hoskins)Tributes at the scene where Jack drowned (Picture: Ellie Hoskins) (Image: Archant)

“He couldn’t process it, he was confused and panicky,” Mrs Susianta explained.

“He said: ‘They’ve kidnapped me. They aren’t really police. They aren’t real, mum’,” she said.

“It was as if he was trying to make me believe what he was thinking, it was obvious he didn’t know what was going on or what he was thinking.”

Mrs Susianta praised the psychiatrist, Dr Spedburg, who gained Jack’s trust and “helped him begin to see reality”, and felt her son was starting to get better.

Hackney Gazette: Tributes at the scene where Jack drowned (Picture: Ellie Hoskins)Tributes at the scene where Jack drowned (Picture: Ellie Hoskins) (Image: Archant)

Later that morning toxicology reports showed Jack had “taken a mixture of drugs”, and consultant Dr Ericksen said there was a bed waiting for him at a children’s mental health hospital in Tower Hamlets, but that she felt he was well enough to go home.

“He had talked lucidly about himself,” said Mrs Susianta. “I was relieved and thought the nightmare was over.

“I didn’t know it was about to begin.”

Jack slept most of that day but by the evening his mother grew concerned again after he became “freaked out by some things on TV”.

“He was getting more and more nervous,” she said.

“I was listening at the door and he was talking to his friend on the Xbox. He said ‘hello’, but then he said: ‘But how do I know it’s really you?’”

The next morning when he woke his mother described him as “fearful”, lying in bed looking at his hands.

His brother took him to play basketball, a sport he would usually play every day, whereupon he said: “If I get a hoop, that means things are going to be alright. If I don’t, it’s not.”

“He didn’t, so he freaked out,” his mother said.

“We didn’t know what to do. Sam was looking on the internet. Suddenly it was the same pattern as Monday – he lay in bed with me for a long time, he was holding onto me for more than an hour. He couldn’t get to sleep, so I said: ‘Let’s go and have some lunch.’

“In the kitchen he held his head in his hands. He just didn’t know what was going on, and couldn’t process anything, I saw footage of him in the canal and he did the same thing – holding his head in his hands.

“He was getting worse and then he just said: ‘Right, I’ve got to go’.”

The front door was locked, so Jack “karate kicked” a hole in the window.

“He did the most amazing jump, and he was just gone. It was the last time I saw him alive,” said his mother.

She called 999 and told them her son had mental health issues and was “scared of the police and trying to get away”.

A manhunt ensued and later that day – July 29 – Jack was being pursued by officers when he jumped into the River Lea near the Kingshead Bridge, off Lea Bridge Road in Walthamstow Marshes. He drowned.

The inquest, which is being heard by a jury, continues.