The latest progress in the investigation into the movements of Anis Amri, from when he fled the truck used to drive into the crowds in a Christmas market in Berlin, to when he arrived in Italy, revealed that the 24-year old Tunisian man travelled through the Netherlands in his journey away from the scene of the tragedy.

Amri was shot dead by two Italian policemen in Milan in the early hours of 23 December, ending a four-day manhunt for the person responsible for the attack in Berlin on 19 December, which killed 12 people. The items found in his possession are helping investigators across Europe understand how he arrived in Italy, what was his final destination and who – if anyone – helped him along the way.

Italian newspaper La Repubblica reported that the Italian police found an unused sim card in Amri's backpack, still in its original wrapping, which could have been obtained in the south of the Netherlands – as it was distributed for free in that area between 20 and 22 December.

Dutch police are now investigating the possibility that the man travelled to France by bus, from the station of Amsterdam Sloterdijk, reaching Lyon in France on 22 December. The Paris prosecutors' office confirmed on 27 December that Amri was filmed at the Lyon Part Dieu train station around midday.

From there, he bought a ticket to travel to Italy on a high speed train departing from Lyon to Milan. Italian media report that the man transited through the small French town of Chambery and then, after crossing to Italy, first got off in the mountainous town of Bardonecchia, taking a regional train to Turin, where he waited for a few hours, and finally one to Milan. Regional trains are usually less controlled than the high speed ones.

Anis Amri
The covered body of Anis Amri, the suspect in the Berlin Christmas market truck attack, lies on a street in MilanReuters

According to Italian media, the police believe that Amri was trying to reach the south of Italy, where he likely knew people from the four years he spent in prison in Sicily. The authorities however doubt he was helped by anyone along the journey across Europe, as he always appeared on his own in the images caught by the security cameras, and suspect he acted as a lone wolf.

In this photo shared by the Italian police Twitter account, the suspect is seen walking through Turin's Porta Nuova train station at 10.14pm (9.14pm GMT) before he boarded the train to Milan.

The police released this image too, which shows Amri walking around Milan central station in the early hours of 23 December.

The investigation is also focusing on the weapon used to shoot one of the Italian policemen who found Amri outside a Milan train station on 23 December, a German-made gun. The 22-calibre Erma Werke, which may be the same used to kill the Polish driver of the truck, who was shot in the head before the attacker took control of the vehicle to plough into the crowd.

A comparison of the bullets will confirm or dismiss that hypothesis, but authorities will nonetheless be looking at how and where Amri was able to acquire a gun.