An Isis militant murdered a police commander and his wife at their home near Paris before being shot dead by officers who rescued the couple's three-year-old boy unharmed.
After killing the couple Larossi Abballa, 25, recorded a 12 minute monologue to camera while in the couple's house in Magnanville and posted the video on Facebook Live.
In the video, Abballa says: "We will come and find you the way I have found this policemen at his house."
He also hinted at an ISIS attack on the Euro 2016 football tournament, saying: "We're keeping another surprise for the Euros but I won't say anything more."
And, chillingly, he also hinted that the son of his victims was also in danger, saying: "I don't know what I'm going to do with the boy."
He continued: "(President) Hollande you are ruthless but we are also heartless...I was ruthless just now towards this policeman and his wife."
Police later raided Abballa's home and found a hit list on his computer which contained six names.
Prosecutor Francois Molins said they included "rappers, journalists, police officers and public personalities".
During Abballa's video diatribe he expressed particular hatred for journalists Bernard de La Villardière, Audrey Pulvar, Mohamed Sifaoui and Lea Salame, political scientist Gilles Kepel and rapper Booba.
Booba is of Senegalese Muslim origin and was, ironically, accused of anti-Semitism in 2014 for the lyrics of a song which appeared to praise Mohammed Merah, a lone wolf who killed seven people, including a rabbi and three Jewish children in Toulouse in 2012.
Abballa called on Muslims to kill journalists and police officers and added: "Target their fear."
He stabbed Jean-Baptiste Salvaing, 42, nine times in the stomach at his home in the Yvelines department, north west of Paris, shortly after 8.30pm on Monday.
After a three-hour stand-off elite Raid commandos entered the building, where they killed Abballa.
Inside the house, they found the lifeless body of Mr Salvaing's wife, Jessica Schneider, who was an administrator who worked for the police force in Mantes-la-Jolie.
The only survivor was the couple's three-year-old son, who was "extremely shocked but otherwise unharmed".
The couple's young son was "in shock but unharmed," a prosecutor added, saying he was receiving medical attention.
Mr Molins said Abballa pledged his allegiance to ISIS three weeks ago and appeared to be following a recent order from ISIS leader Abu Bakr al-Baghdadi "to kill miscreants at home with their families" during Ramadan.
Three men - "linked to" Abballa - were arrested on Tuesday morning. They were described as 'acquaintances' and are aged 27, 29 and 44.
It also emerged today the knifeman was part of a recent investigation into a Syrian jihadist network.
French security expert David Thomson said Abballa posted gruesome images of the murdered couple on the internet.
A 12-minute video and 15 photographs appeared on Abballa's Facebook page, along with his justifications for what he had done.
Abballa's Facebook profile, under the name Mohamed Ali, was suspended in the early hours of this morning.
Mr Thomson told a Paris radio station that at one point Abballa could be seen sitting on the sofa with the child behind him.
Abballa wrote: "I still don't know what I'm going to do with him."
One of his most recent Facebook posts was a mock-up of the European Championship logo, which he claimed contained masonic and occult symbols.
Abballa was born in Mantes-la-Jolie, a suburb close to the scene of the killings.
He had criminal convictions for theft and violence dating back to 2011.
Abballa earned a living as a restaurant delivery man and used the moniker Doctor Food.
Mr Thomson said he frequently used social media to call for the murders of police, prison officers and journalists, often by name.
Abballa had also been sentenced in 2013 for taking part in a jihadist organisation with links to Pakistan.
He was sentenced to three years behind bars, six months of which were suspended for "criminal association with the aim of preparing terrorist acts" following a trial with seven other defendants.
Despite this, he only spent a few months in prison, and is thought to have maintained his links with a group sending jihadists to fight in Afghanistan.
It has also been revealed Abballa had previously claimed allegiance to ISIS and sources say he did so again while talking to officers during the siege.
The terror group's al-Amaq news agency said the attacker was an "Islamic State fighter" and claimed responsibility for the killings.
Witnesses told investigators the man may have shouted "Allahu akbar" (God is greatest) as he stabbed the policeman repeatedly.
President Francois Hollande held a top-level security meeting to discuss the "appalling terrorist act" which took place as France was on high alert for the Euro 2016 football championships.
He said: "France is not the only country concerned as we have seen, again, in the United States, in Orlando."
Mr Salvaing was an assistant chief with the judicial police at nearby Les Mureaux.
The French police have set up an online book of condolences for Mr Salvaing and Ms Schneider.
The killing came a day after a gunman claiming to be acting in the name of ISIS shot dead 49 people at a gay nightclub in Orlando, Florida, in the worst mass shooting in US history.
Yves Lefebvre of police union Unite SGP Police-FO said: "Today every police officer is a target."
He said terrorists were getting more "professional" and were able to track down police officers to their homes.
The bloodshed also comes as France hosts the Euro 2016 football tournament under tight security, still reeling from jihadist attacks in Paris last November that left 130 people dead.
Loud detonations were heard at the scene as RAID officers moved in following failed negotiations with the attacker.
Officers found the woman's body when they stormed the building, and the attacker was killed during the assault.
Mr Molins said inside the house police found three mobile phones and three knives, including one which was covered in blood.
Interior Minister Bernard Cazeneuve expressed his "infinite sadness" at the death of the police commander and his partner, who had worked for his ministry.
"The attacker was neutralised by RAID forces, who showed great composure and great professionalism and who saved the couple's little boy," Cazeneuve said in a statement.
"The inquiry opened by the justice authorities will establish the precise circumstances of this tragedy."
Police sources said earlier in the evening that the attacker had taken the policeman's partner, who worked as a police secretary, and son hostage after stabbing the officer to death as he returned home around 9pm.
Residents were evacuated from the neighbourhood as police moved in.
RAID officers "arrived rapidly on the scene. Negotiations were launched and an assault plan was put in place," said Brandet.
But the negotiations were "unsuccessful" and authorities decided to launch an assault around midnight, he added.
A helicopter was on the ground a few hundred metres away from the scene of the attack, while several fire trucks and ambulances were seen leaving the security perimeter.
President Hollande said in a statement that he "strongly condemned this odious act".
"A police commander and his partner, a civil servant at the interior ministry, were shamefully murdered this evening," Hollande said.
"All light will be shed on the circumstances of this terrible tragedy," he added.