The body of Anis Amri, the suspect in the Berlin Christmas market truck attack, is seen covered with a thermal blanket next to Italian officers in a suburb of the northern Italian city of Milan, Italy December 23, 2016. REUTERS/Stringer

PARIS (Reuters) - The Tunisian suspect behind the truck attack that killed 12 people in a Berlin Christmas market last week appears to have passed through Lyon in France as he fled to Italy, a French judicial source said on Monday.

Video surveillance footage showed Anis Amri at the Lyon-Part-Dieu train station on Thursday, and officials believe it was at the station that he bought a ticket for Chambery, the source said, between Lyon and the Italian border.

Amri was shot dead near Milan in Italy in the early hours of Friday after he pulled a gun on police who had asked for his identification papers.

French officials are investigating how he arrived in Lyon after the Dec. 19 attack in Berlin that has been claimed by the Islamic State.