The French gendarme who took the place of a female cashier held hostage in a supermarket in France by a radical Islamist who had already killed three other people was a devout Catholic who married his partner on his deathbed.

Lieutenant-Colonel Arnaud Beltrame has been hailed as a sacrificial hero by senior church, police and political figures including Pope Francis, the French president Emmanuel Macron and US President Donald Trump after he died following the attack in which he swapped himself for a hostage in the southern town of Trebes, near the medieval city of Carcassonne.

Now it has emerged that the 44-year-old, who returned to practising his Catholic faith in his 30s after a conversion experience, was to have a church wedding in three months, having already married in a civil ceremony. The priest who was meant to be the couple's celebrant reportedly rushed to his bedside and read him his last rites before he died. The priest, identified as Father Jean-Baptiste, also said he married the man to his wife before he died, according to The Sun.

Beltrame died on Saturday (March 24) from shot and stab wounds during the siege.

'A life that has been given cannot be lost,' said Bishop Alain Planet of Carcassonne and Narbonne at a memorial Mass in Trebes yesterday.

'It transcends misfortune to rally us in unity. It calls us to believe in life stronger than death.'

According to The Tablet, Bishop Planet said that people who compared him to Saint Maximilian Kolbe, the Polish Franciscan priest who volunteered to be executed in Auschwitz in place of a family man, 'have understood something of his act, even if the circumstances are different'.

In his Palm Sunday sermon, Archbishop Georges Pontier, president of the French bishops conference, compared Beltrame's act to 'the gesture of Jesus who gave his life for us'.

Macron praised the gendarme's 'exceptional courage and selflessness'.

A national memorial service is planned later in the week.

'He died a hero,' said Macron in a statement that noted Beltrame had served as a paratrooper in Iraq, head of a Republican Guard security company at the Elysée Palace and intelligence advisor at France's ecology ministry before taking command of the local gendarmerie in Carcassonne.

Meanwhile, Fr Jean-Baptiste recounted in a statement that, for almost two years, he had helped Beltrame and his wife prepare for their church wedding which was set for June 9.

The priest found him still alive but unconscious when he arrived at the hospital. 'I was able to give him the sacrament of the sick and the apostolic blessing at the hour of death,' he wrote. 'I think that only his Christian faith, animated by love, could have demanded of him this superhuman sacrifice.'

Beltrame regularly attended mass at the abbey, the priest said.

The gendarme's mother, speaking before her son died, told RTL radio he had constantly thought of serving his country and helping others. 'He was always like that...he would tell me "I'm just doing my job, Mum, that's all."'

Islamic State claimed that the attacker – Radouane Lakdim, 25, born in Morocco – was answering its call to target nations in the coalition fighting ISIS in Syria and Iraq.

Today, it emerged that Pope Francis sent a message of condolence to Bishop Planet, expressing his sadness over the attack, entrusting the victims to God's mercy and praying for the families of the victims.

'I particularly recognise the generous and heroic act of Lieutenant-Colonel Arnaud Beltrame who gave his life out of a desire to protect people,' the Pope told the bishop.

'I condemn again such acts of indiscriminate violence which cause so much suffering.'