A student and climate activist died after growing “increasingly concerned” about the effects of climate change, his family have revealed.

Theo Khelfoune Ferreras was a committed campaigner against climate change and a supporter of animal rights during his time as a student at Brighton University.

The 19-year-old film student, who worked for Greenpeace, was found dead in Wild Park at the end of last month.

Now, his sister has told the Guardian's sister paper The Argus that Theo's concerns for the environment took a toll on his mental health and caused him to lose hope in the future.

Lisa Khelfoune, 18, from Walthamstow, said: "He was so into activism and really believed he could make a difference.

“He wanted to contribute to a change in society and tried to live according to his values; he wore mainly second-hand clothes, rode his bike everywhere, he walked frequently in forests and natural reserves.

“I think he had a complete feeling of helplessness. Theo felt like what he was doing was futile and he lost hope in the future and this devastatingly affected his mental health.”

Lisa paid tribute to Theo, a graduate of the Brit School, who was “passionate about photography” and was a part of the Brighton music scene.

Following his death, the family were able to “miraculously” locate Theo’s bike, something Lisa described as “very symbolic and meaningful” for the family.

Lisa has now setup a GoFundMe page to help give her brother an eco-burial in Epping Forest.

She said the fundraiser was a “welcome distraction” and “mind-blowing display of human compassion”.

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Before his death on March 29, he had plans to travel to Cuba to attend film school and wanted to specialise in documentary making.

Recently, Theo had become a fundraiser for Greenpeace and had also spent time restoring a cultural centre in London.

Will McCallum, co-executive director director of Greenpeace UK, said: “We were shocked and saddened to hear of Theo’s passing. Our hearts go out to their family and friends at this difficult time.”

Visit https://www.gofundme.com/f/theo-khelfoune-ferreras to donate to Theo's eco-burial.

Last month, The Argus reported how emergency services had been called to an incident in Wild Park.

A witness described seeing "at least four" police cars and numerous ambulances at around 3pm.

Sussex Police said they were called following concerns for a person's welfare and there was "not considered to be any wider risk to the public".

Samaritans (116 123) operates a 24-hour service available every day of the year.

If you prefer to write down how you’re feeling, or if you’re worried about being overheard on the phone, you can email Samaritans at jo@samaritans.org.