The Dubrolle wood was until a few weeks ago the site of a large makeshift camp for migrants hoping to sneak into Britain on ferries heading for the UK coast.
Chloe's mother, Isabelle, who was present, burst into panicked screams as the man, described by witnesses as bald and wearing sunglasses, shoved her daughter into his car.
"I ran around the building calling out for Chloe. I saw her lying on the ground behind the bins. And then the bloke, who I only saw from behind, took her in his arms and took her with him to his car, which started straight away. It was too fast. I was only a few metres away with my other children, but I couldn't do anything. I was petrified."
She added: "I am starting to realise that I will never see Chloe again. I don't know how I'm going to tell her little sister and brother."
Police were alerted to the kidnapping at 3.30 pm and search teams were dispatched, one of which made the grisly discovery of the murdered child at 5pm.
Forensic investigators reported evidence of "strangulation and sexual violence", said Mr Valensi.
Nearby, police found the red vehicle with Polish number plates, and the driver - heavily under the influence of alcohol - was arrested not far from the scene on foot.
The suspect "immediately admitted his involvement in the child's death," said Mr Valensi.
Huminski had been banned from French territory after being convicted twice for acts of 'extreme violence' including attacking a pensioner with a knife.
But he had driven to France in a Polish registered car this week, and intended to travel to Britain to stay with family who had emigrated there, said Mr Valensi.
Mr Valensi said that Huminski had been given a four-year jail sentence in 2004 for armed robbery. In 2010, the Boulogne criminal court gave him a six-year sentence for sexually assaulting two women and a girl, and banned him from living in France after his release from jail.
But the ban did not comply with French law and had never been enforced , Mr Valensi said. When Huminski was freed in 2014 he was transferred to Poland, where he was wanted for questioning in connection with burglaries, but allowed to return to France.
Chloe's mother said that she was "sickened and disgusted" at the failure to expel him. "I can't understand why he was in France," she said.
Nathacha Bouchart, the mayor of Calais, said: "How could a foreigner with many previous convictions be allowed to move freely around Calais? There is a clear dysfunction in the way we keep track of repeat offenders."
It also emerged on Thursday that he had already threatened another little girl in 2009.
David Selingue, a hairdresser in Calais, said his wife found the Pole in the room of his nine-year-old girl in June of that year, emerging from under a piece of furniture with a knife.
"He was pointing the blade towards her (his daughter) to threaten her," Selingue told AFP, adding he then escaped through a window.
"He is bad, a predator, he observes and then acts."
Around 5000 people took part in a solemn march in memory of Chloe on Thursday evening, while flags were at half-mast in the town.
Speaking to the mourners, Chloe's mother said: "Chloe was just a child. Chloe was nothing but joy. Today we all mourn a child that just wanted to live. A terrible and unjust fate has cut this child down who will never be returned to us."
