A former Royal Marine who was shot dead while fighting against Islamic State in Syria was "horrified by the atrocities being carried out by IS".
Konstandinos Erik Scurfield, from Barnsley, South Yorkshire, is believed to have travelled to Syria three or four months ago hoping to provide medical and humanitarian support.
He was killed on Monday while fighting alongside Kurdish forces in the frontline village of Tel Khuzela, Kurdish commander Redor Khalil said.
Mr Scurfield, who was an expert in battlefield medicine, is the first Briton to be killed while fighting IS in Syria.
His family said they were "reeling" after receiving the news, which was described as "heartbreaking" by friends.
Mr Scurfield's family had recently spoken to Barnsley Central MP Dan Jarvis about their fears for his safety.
The Labour MP, who raised the issue in Parliament last month, said their "worst fears had been realised".
He said: "My first thoughts are with the Scurfield family.
"They came to me a few weeks ago very worried for their son's safety and tragically it appears their worst fears have been realised."
Mr Jarvis added: "Erik was an experienced former Royal Marine who was horrified by the atrocities being carried out by ISIS.
"His family's understanding was that he travelled to Syria hoping to provide medical and humanitarian support as an expert in battlefield medicine."
Vicci Scurfield, the ex-Royal Marine's mother, told Sky News that the family, who live in a detached former farmhouse in the village of Royston, SouthYorkshire, was "reeling".
The family did not want to say anything else as they returned home this morning but neighbours described their shock at the news.
Mary Jane Hemmings said the news was "heartbreaking".
She said: "I've been so shocked. I really am terribly, terribly upset.
"It doesn't surprise me that he went because he seemed to do everything 100% and he seemed to have deep feelings. He was very conscientious, he was a lovely person."
She added: "He was a very strong-willed man, I would say, and he knew what he was about. I am sure he knew what he was doing."
Neighbour David Miller said Mr Scurfield's parents, Chris and Vicci, are archaeologists and his sister, Georgianna, was a student.
Dr Miller said: "It's tragic."
He added: "The children moved away and I'm not sure how Erik got involved in Syria but it would be in keeping with their sense of duty and honour.
"They are good British people and it would make sense that he would go all the way to Syria to fight against ISIS."
Mr Scurfield was named yesterday by the Kurdish People's Protection Units (YPG).
A statement on the Kurdish Question website read: "We can confirm that Konstandinos Erik Scurfield died in battle, probably in Hasakah although the full details are yet to be announced by YPG."
Mark Campbell, a pro-Kurdish rights campaigner, said he broke the news to Mr Scurfield's mother.
He said: "It was just awful, to be honest. Just to receive a phone call withthat sort of news was just devastating.
"It was so incredibly difficult, it was very, very emotional, she was literally in tears the whole conversation.
"I really just wanted to inform her, to give her a message from the YPG that they have said they would love to bury Konstandinos as one of their comrades in arms, as a hero, but equally they also want to be guided by the family and will respect the wishes of the family."
Mr Campbell said Mr Scurfield's death also had a great impact on his friends and colleagues.
He said: "I've got a message from Jordan Matson saying that he is lying with his (Mr Scurfield's) body.
"I think he's been incredibly affected by his death as well, I think he was one of his closest friends."
Mr Matson, believed to be a former US soldier fighting with the Kurds, paid tribute on Facebook to Mr Scurfield, describing him as a "disciplined warrior".
He posted: "Words cannot describe how honored I have been to fight at your side Sehid Kemal (Konstandions Erik Sculfield).
"We were together from his first day here and you couldn't ask for a more disciplined warrior.
"Kosta, as we call him, was from the United Kingdom and was born a Greek citizen. He served both in the Greek army and as a British Royal Marine commando up until he came here. He served with me in Jezza and Shengal.
"Kosta volunteered for every attack and guard duty opportunity. He wanted nothing more than to bring the fight to the enemy.
"I'm going to carry on your legacy, brother, I will never forget you. I love you, man. Save me a place up there, big guy."<
Mr Campbell said he thought Mr Scurfield had been in Syria for three to four months.
He said he believed Mr Scurfield had seen what was happening in Syria and was "frustrated" that the UK Government was not helping the Kurds fight IS.
He said: "The people are just going there with this feeling of frustration that the UK Government is not doing anything."
He added: "If the Kurds are left to fight alone, and I think that's the feeling people have, they want to help in some way and they go there.
"And because the war is continuing and these battles are going on every single day, if there's no support for them I think possibly we will hear of more of these tragedies."
While high numbers of foreigners are known to have joined IS, around 100 Westerners - including several Britons - are thought to have fought alongside the Kurds.
Last month, a 19-year-old serving British soldier was returned to his unit after joining the Kurdish peshmerga.
It was reported that he left his base after telling his family he was joining the Kurdish military forces in their battle against IS because "these guys need our help".
In a letter to his family he claimed to have met other British people and a Canadian while there.
In December it emerged that two former British soldiers had travelled to Syria to fight against IS after feeling "compelled" to take up arms following the murder of aid volunteer Alan Henning.
A Foreign Office spokesman said: "We are aware of reports of the death of a British national in Syria.
"The UK has advised for some time against all travel to Syria, where all UK consular services are suspended.
"As we do not have any representation in Syria, it is extremely difficult to get any confirmation of deaths or injuries and our options for supporting British nationals there are extremely limited."