The French jihadist who shot dead four people in a terrorist attack at a Jewish museum has been sentenced to life in prison by a Brussels court, after prosecutors branded him a coward and a psychopath.

Mehdi Nemmouche was convicted last week of “terrorist murder” for the antisemitic gun rampage in the Belgian capital in May 2014 after his return from Syria.

He was found to have killed the four victims in less than 90 seconds, shooting them with a handgun and a Kalashnikov rifle with what one paramedic who attended the scene called “surgical” precision.

Before jurors retired to consider the sentence on Monday, the 33-year-old smiled and told the Brussels criminal court “life goes on”.

The court, which handed down the sentence in the early hours of Tuesday morning, said the 33-year-old had shown no regret for the killings.

“Mr Nemmouche, you are just a coward. You kill people by shooting them from behind, you kill old women by shooting them with an assault rifle, you kill because it gives you pleasure to kill,” Yves Moreau, prosecuting, had said.

Urging the jury to take a firm line, Moreau said: “If you say that in Belgium one can be a terrorist without being punished very severely, then we must not be surprised to see people arrive in this country with bombs or assault rifles in their suitcases.”

Nacer Bendrer, who was found guilty of being the co-author of the attack for supplying the weapons Nemmouche used, was given a jail sentence of 15 years.

Bendrer, who is also French, said he was ashamed he had ever met Nemmouche, saying: “He’s not even a man, he’s a monster.”

The pair, who have 15 days to lodge an appeal, will serve their sentences in France.

The investigation showed the two men had dozens of telephone conversations in April 2014, when Nemmouche was preparing for the killings.

Six days after the shooting, Nemmouche was arrested in Marseille in possession of a revolver and a Kalashnikov-type assault rifle.

Among the victims of the attack were an Israeli couple, Miriam and Emmanuel Riva. Nemmouche claimed the couple were agents of the Israeli intelligence service Mossad who had been hunted down and killed by someone else.

He denied responsibility for the shootings and said he had been “trapped”.

On Tuesday, a lawyer for the murdered couple said the sentence was “fair and proportionate”.

Prosecutors say the attack was the first carried out in Europe by a jihadist returning to the continent after fighting in Syria.

Nemmouche, who was brought up in foster care, has become a case study in the radicalisation of young European Muslims. Belgium and France, in particular, fear the defeat in Syria of groups such as Islamic State will lead to the return of more angry young men to Europe.

During his time in the war-ravaged country, Nemmouche is accused of acting as the jailer of four French journalists taken hostage by jihadists in Aleppo in 2013. Two of the journalists who travelled to the court to give evidence said they had no doubt it was him.

He is due to go on trial in France over the hostages at a later date.