Mnihla Tunisia:On Tuesday morning Houssam Abdelli quickly finished his coffee at a cafe on the outskirts of Tunis where he and his friends would gather to watch their favourite football players in action.

Hours later he boarded a bus carrying presidential guards to work along one of the capital's main thoroughfares clasped the detonator of his 10-kilo Semtex explosive vest and blew himself up.

Abdelli a 26-year-old street vendor was formally named this week by investigators as the man who killed 12 guards and wounded 20 people including four civilians.

Friends and neighbours in the Cite al-Joumhouriya district of Mnihla a northern suburb of Tunis spoke of their shock that Abdelli could be capable of inflicting one of the worst ever attacks on Tunisia's security forces.

"Houssam was a football fan. He supported Club Africain" one of Tunis' most successful teams said Walid 27.

"We often went to the cafe to play cards and watch Spanish league games. He was also a very good football player to the point where we nicknamed him Pereira" after the Brazilian defender Fabio Pereira.

According to residents who spoke to AFP Abdelli's family is "not particularly poor". When he quit high school as a teenager his father built an annex to the family home so Houssam could "settle and get married".

A neighbour who asked not to be named described him as "a polite young man who always said hello to everyone".

But friends recall Abdelli undergoing a gradual change withdrawing more and more from society and shunning the alcohol and drugs he had once dabbled in.

About a year ago locals noticed Abdelli had stopped being so approachable.

"I spoke to his father and he told me that he had changed after becoming very religious" the neighbour said.

According to Walid Abdelli had "turned totally in on himself".

"Before we had a few drinks together and smoked cannabis. Suddenly he became another person and visited a mosque that was controlled by Salafist jihadists" he said.

"But no one can believe he could carry out such an atrocity."

August arrest

IS's claim of responsibility for Tuesday's attack -- which follows deadly assaults on Tunis's National Bardo Museum in March and at a Mediterranean holiday resort in June -- included a picture of Abdelli virtually unrecognisable to his friends.

He appears to be wearing a suicide vest his head shrouded in a white scarf with one finger pointing skywards.

Friends recount a number of disputes Abdelli had in recent months.

"One day he met me and called me a 'devil' because I was drinking alcohol. I was very upset but I didn't respond because I know his father is a good man" said Mehdi who only gave his first name.

A cafe waiter said Abdelli "had a fight with one of his neighbours who works for the presidential guards. He called him 'taghout'" -- tyrant in Arabic -- a term used by extremists when describing security forces.

"Last Tuesday he came as usual in the morning drank his coffee fast and left without saying a word" the waiter said.

That night residents of Cite al-Joumhouriya were plunged into mourning: one guard killed in the attack Amour Khayati was from the neighbourhood.

Interviewed by local television the family said they suspected Abdelli had followed Khayati's movements for several days leading up to the attack.

A security source told AFP that Abdelli had "pretended to be a street vendor in order to spy on the houses of police".

"At the start of November he photographed the residence of a National Guard officer and marked the spot. The officer's wife saw him and he fled. She identified him from a photograph" the source added.

Another warning sign according to a neighbour was that Abdelli had been detained by police in August.

"We heard that he tried to go to Syria but had been stopped" she said.

Another security source told AFP that extremist literature had been seized from Abdelli after his arrest.

"We arrest these potential terrorists but the courts free them" the source said.

AFP