Relatives and community leaders say they are praying that a Briton was not behind a suicide bomb attack on a prison in Syria.
Abdul Waheed Majeed, 41, is suspected of being responsible for driving a lorry into a jail in Aleppo and detonating a bomb last week.
Officials have not confirmed the identity of the bomber amid reports that a UK jihadi, who used the name Abu Suleiman al-Britani, carried out the bombing.
It is thought to be the first time a Briton has staged a suicide attack in the war-torn state, where rising numbers of UK-born extremists have gone to fight.
Counter terrorism officers were searching Majeed's home in Martyrs Avenue in Langley Green, Crawley, West Sussex - the ex-home of schoolgirl Sarah Payne's killer Roy Whiting, according to neighbours.
Married father-of-three Majeed, known as Waheed, left Britain six months ago, telling his family he was going on a humanitarian mission to Syria.
Arif Syed, a community leader in Crawley, said Majeed would phone or Skype his family every three days, but communication was lost with him about seven days ago.
UK counter-terrorism teams have grown increasingly concerned about the trend of young Britons travelling to Syria to train to fight with jihadi groups, and the potential that they could return and stage attacks on UK soil.
Mr Syed, 59, said he hoped to learn that Majeed was not behind the attack in Aleppo. He said: "We have got our hopes high.
"We are praying that he will walk through the door. It's a good possibility that he's still alive and well, and is just not communicating.
"We live with this hope until the authorities confirm, or we get eye-witnesses that say it was him. We strongly hope and believe that he is alive and well, and that he will join his family."
Majeed is a father of two boys and a girl aged 18, 16 and 12. He was born and bred in Crawley and worked as a highways contractor.
His uncle, Mohammad Jamil, 65, said Majeed had never shown any sign of extremism. He said: "If the family knew about this, we wouldn't have let him go."
Majeed left for what was said to be his first humanitarian mission to Syria in August, and had not indicated when he would return to Britain.
Mr Syed said he missed two opportunities to return, the last in early January. He said: "He enjoyed it so much and he extended his period of stay."
Mr Syed said the police informed the family that they could not confirm through their intelligence that Majeed was definitely responsible for the bombing.
He said: "The family has been in constant touch with him for several weeks, and he has been sending photographs.
"He has mostly been working with a charity on the refugee camps and distributing aid which he has collected from here and other towns in the UK.
"He was quite happy and enjoying this piece of work. We had communication until about seven days ago.
"He had said he was going to another camp and there might be switch-off with the communication, which has happened before.
"He said 'If I don't contact you for a few days, don't worry about it, I will be in touch again'. That's the last communication we had."
When news emerged about the suicide bombing in Syria, the family of Majeed - who is of Pakistani descent - started to panic, Mr Syed said.
He said: "They started getting really worried as they hadn't been in contact. Also, what happened over the weekend started alarm bells.
"We had a meeting with agencies, including the local authority and the police, yesterday. They told us that they couldn't confirm through all their intelligence and sources that it is this man or not.
"As far as we are concerned, the man reported on the internet and social media is Abu Suleiman al-Britani.
"We have a very close community in Crawley and it is a very diverse town. We don't recognise that name. We have asked every member of our community if they recognised (this name) and they don't."
Mr Jamil said Majeed's family hoped for positive news from the authorities and that he will eventually turn up alive and well.
He said: "The bottom line is that the police cannot confirm it, there is no confirmation and the family has got hope that as long as there is no confirmation, we hope that he will turn up."
Mr Jamil said relatives had been co-operating with the police and were left "shocked and surprised" when they obtained a search warrant to raid Majeed's family home.
"There was no need for it," he said. "The family was co-operating. They should have taken a bit more of a sensitive decision.
"This happened miles away and the family is feeling the brunt of it. I think that was unnecessary."
Mr Jamil said the family had no reason to believe that Majeed was anywhere but at refugee camps giving aid.
Describing his nephew as a "family man", h e went on: "He spent a lot of time with his wife and kids and he has always been employed, and a well-liked person."
The emotions of Majeed's wife have fluctuated since reports suggested her husband might be behind the suicide bombing, Mr Syed said.
He said: "When people believed it was him, she went through a period of bereavement.
"When we gave her the information that the agencies could not confirm, she was really delighted, but she is in a totally confused state."
A police officer stood guard outside the family's two-storey, end-of-terrace property in a residential part of Langley Green.
Neighbour Nita Bateman said Roy Whiting, who murdered eight-year-old schoolgirl Sarah Payne in 2000 in West Sussex, used to live at the house.
Ms Bateman, 55, expressed shock at the revelations that the house could have been used by a suicide bomber, describing him as a "pleasant chap".
She said: "When I became very ill, he was always willing to help, and he would do my neighbour's hedges.
"I'm beginning to wonder whether it's something to do with that house. He was the next person to move in after Roy Whiting's dad moved out.
"I know he was born in West Green, just up the road from here. I have lived here for 20 years, and after all the hoo-ha with Roy Whiting, he moved in soon afterwards.
"I didn't really see him on a daily basis, but you would never have a bad word to say about him - he was just a pleasant chap.
"I would say I'm shocked, but you just don't know what goes on behind closed doors."
Ms Bateman said she would often see the man drive to work in a motorway maintenance lorry. She believed he had a wife and at least one child.
She went on: "Whenever we saw each other, he would acknowledge me and I would him."
Another neighbour, who declined to be named, said: "He was just a quiet guy. Whenever I saw him, he was either working on his car or doing other stuff.
"Sometimes I would see him drive off in a maintenance lorry. Whenever I saw him, I would nod my head and say hello.
"We have been living here for more than 12 years, so he has been here longer. It was a shock when I found out because he was a nice guy, but I don't know much about him."
A brief statement from the south east counter terrorism unit said: "The south east counter terrorism unit is searching an address in Crawley as part of our ongoing inquiries regarding the suicide bomber at Aleppo prison."
A Foreign and Commonwealth Office spokesman said: "We are aware of the reports that a British national died in Aleppo in a suicide but we are unable to confirm that."