THE man detained on suspicion of killing a popular Spanish student in Bournemouth is 29-year-old Karl Addo.

He is understood to have lived with victim Sergio Retamar Marquez for the past two months at the Lansdowne flat, where Sergio, 23, was found decapitated last week.

Mr Addo is believed to be being held outside Dorset after being bailed to a secure unit last week.

His twin brother, Conrad, contacted the Daily Echo on Friday evening, telling us he had only learned of the incident on Thursday evening, two days after his brother’s arrest.

It is understood Mr Addo grew up in the United States in Georgia and Atlanta, transferring from the Georgia Institute of Technol-ogy to Queen Mary University of London where it is believed he studied aerospace engineering from 2008-2010.

The website, which lists information people have posted about themselves, says he was a publishing intern at the Royal Society for a month in the year 2009.

It also lists his interests as racing karts, working on motorcycles, football, running and road bike racing.

Over the weekend, shocked residents, still coming to terms with the incident, remembered seeing Mr Addo around the Lansdowne area.

One man, who did not want to be named, said he thought he had lived here for around the same amount of time as Sergio.

He said the pair appeared to be flatmates rather than friends, with Sergio moving in first and Mr Addo following soon after.

Another man, who works near to the flat where Sergio’s body was discovered, said he had seen Mr Addo walking around but did not know him to speak to.

“When I saw him recently, his hair was shorter and he looked to have dyed it a gingery colour,” he said.

Staff and customers at Sonia’s House restaurant, around the corner from Downes, remembered Mr Addo.

One female worker, who asked not to be named, said: “He would stand outside the door and watch our TV.”

She added: “He was walking around all the time.

“ I saw him so many times, he was always looking into the restaurant.

“The other businesses said exactly the same”.