Police arrested Zbigniew Huminski, 38, on Wednesday, hours after kidnapping, raping, and killing the girl.

The girl, identified by her first name as Chloe, had been playing in a small park before being violently abducted by Huminski after she sprayed water on him from her pistol as he drank a beer, said prosecutor Jean-Pierre Valensi.

Thousands of citizens marched through Calais yesterday to express support for the family and outrage.

Valensi told reporters the body of the 9-year-old showed she was strangled and sexually assaulted after Huminski threw her in his car and took her to a nearby woods. Valensi said that Huminski admitted “immediately” to the killing after his arrest.

Authorities are trying to unravel Huminski’s tangled judicial past and establish how a man convicted twice, in 2004 and 2010, then outlawed from France, apparently returned.

The prosecutor said France was, in the end, unable to force Huminski out of the country on the basis of his past convictions for extortion with violence, aggravated theft and sequestration.

However, he was handed over to Polish authorities last year based on a European arrest warrant for a 2000 robbery in Poland. The warrant was issued in 2010.

French justice minister Christine Taubira demanded a “complete, precise, rapid” investigation.

“What we owe the family is the entire truth,” said French prime minister Manuel Valls.