BRUSSELS (Reuters) - Brussels suicide bomber Najim Laachraoui was a nice, intelligent boy, his brother said on Thursday, and gave no warning signs of being radicalised before he left for Syria in 2013 and broke all contact with his family.

A man, who police said is named Najim Laachraoui is seen in this undated photo issued by the Belgian Federal police on their Twitter site, on suspicion of involvement in the Brussels airport attack, on March 23, 2016. REUTERS/Belgian Federal Police/Handout via Reuters

Laachraoui, a 25-year-old Belgian, was one of Tuesday’s suicide bombers, security sources have told local media. A veteran Islamist fighter in Syria, he is also suspected of making explosive belts for last November’s Paris attacks.

No one in the family saw any change in his attitude before the day he called them to say he had left for Syria, his 20-year-old brother Mourad said. They also have no clue as to what could have led him to be radicalised, he said.

“He was a nice boy, and above all he was clever, that’s what I remember of him,” Mourad said of his brother, who graduated in electromechanics. The last time he saw Najim, he told a news conference, he looked “normal.”

The family warned the police in 2013 when Najim told them he was in Syria, Mourad said. The police visited them at the time and came back to search their home after the November 2015 Paris attacks.

Mourad, who said he was deeply saddened by the November attacks, said he never saw his brother with their suspected mastermind Abdelhamid Abaaoud, another Belgian, or anyone else involved in the Paris or Brussels carnage.

Najim was religious, as is the family, Mourad said, adding that he would do everything possible to make sure his three younger siblings still at school do not become radical.

Mourad is a taekwondo athlete who has represented Belgium in European and world competitions, Belgium’s ABFT taekwondo federation said on its website.

“It’s crazy, really - the same parents, the same upbringing, and one turns out really well and the other really bad,” his lawyer Philippe Culot said. “Mourad and his whole family are crushed that Najim could have committed such a barbaric act.”

“You don’t choose your family,” Mourad remarked.

Authorities have not officially said that Najim is dead and his family has had no confirmation either, Mourad told journalists.

“VERY GOOD STUDENT”

Najim Laachraoui was a model student in a Brussels Catholic high school, its director told Reuters earlier on Thursday.

“Najim Laachraoui was a very good student,” said Veronica Pellegrini, the director of the Institut de la Sainte Famille d’Helmet, a Catholic school in the ethnically mixed east Brussels borough of Schaerbeek.

“He never failed a class,” Pellegrini said of Laachraoui, who studied at the school for six years, until graduating in 2009. “We haven’t heard from him since,” she said.

Traveling under the false name Soufiane Kayal, Laachraoui was documented driving from Hungary into Austria in September in a car driven by Salah Abdeslam, the prime suspect in the Paris attacks who was arrested in Brussels last week.

There is speculation Laachraoui had just returned from Syria, possibly by sea with refugees.

Catholic religion classes are part of the school’s curriculum for all students regardless of their religion and Laachraoui would have attended those classes as any other student, Pellegrini said.

It is not uncommon for Muslim pupils in Belgium to go to Catholic schools, which can be seen as more conservative or more exclusive than state schools.