Media playback is unsupported on your device Media caption Sally Evans said her son Thomas had converted to Islam as "he believed he would go to paradise"

The mother of a British man killed while fighting for Islamist militant group al-Shabab in Kenya has told the BBC her "whole world has fallen apart".

Sally Evans, from Buckinghamshire, said a journalist had phoned to tell them Muslim convert Thomas, 25, had died.

Her other son Michael said that when he looked on Twitter, the first thing he found was a picture of Thomas's body.

"We remember him as being my brother, your son," he told the BBC. "But to everyone else he's just a terrorist."

Kenyan officials have confirmed that Thomas Evans was killed on Sunday when al-Shabab fighters attacked a military base in the north of the country.

He did say if the worst thing happened, I wasn't to cry because he would be going to paradise, but somehow I cannot celebrate that Sally Evans, Thomas Evans's mother

Militants armed with AK47s and grenades raided the base in Lamu County, close to the Somali border, and then stormed a nearby village.

Eleven gunmen were killed in total and two Kenyan soldiers also died.

'Twisted views'

Evans, who had changed his name to Abdul Hakim, contacted his family in 2012 to say he had travelled to Somalia to join the militant group.

At least 50 British citizens are believed to have joined al-Shabab, an al-Qaeda affiliate based in Somalia, which has been behind a series of high-profile attacks in Kenya and Somalia.

Ms Evans, from Wooburn Green, said she would remember her son as "the little boy who had a bright future before he went down the path he went down".

She said he had met "some people with some very twisted, warped ideas of Islam" in the local area to begin with, and was later influenced by online material.

Image copyright INS News Agency Image caption Thomas Evans changed his name to Abdul Hakim

"I'm very angry that they were prepared to put my son on the line but they are still here," she said. "They are not brave enough to go out there themselves."

Jahan Mahmood is a former counter-terrorism adviser to the Home Office who knows the Evans family.

He said Thomas had been suffering from depression and "stressed out" with personal issues when he was approached by a group of "young Muslims", who did not belong to a particular mosque and had a "very poisonous interpretation".

"These men found him at a vulnerable time in his life, which is often the case," he said.

"This is a cycle that seems to be repeated again and again."

Michael Evans said his brother had changed from the "fun and loving" person he had grown up with.

Lost track

At the age of 21, Evans announced he was moving to Kenya and bought a single plane ticket.

He was turned back at the airport by police, but later sold his CDs and other possessions and told his family he was travelling to Egypt.

In August 2011, police told the family they had lost track of him. The following January he called and said he had joined al-Shabab.

Ms Evans repeated her claim that the British authorities had not done enough to stop her son from travelling to Egypt.

"If they had suspicions, why didn't they involve me?

"We could have worked together to save him and I wouldn't be in this situation now," she said.

Image copyright INS News Agency Image caption Thomas Evans flew to Egypt in 2011 after being stopped from going to Kenya months earlier

"They should have taken his passport. If I'd have known, I would have taken his passport but when they let him fly to Egypt, I thought there was nothing to worry about."

She said she did not know who to turn to for advice and help.

"He would never tell me what he was doing," Ms Evans said.

"He did say if the worst thing happened, I wasn't to cry because he would be going to paradise, but somehow I cannot celebrate that."