Police are today piecing together what happened before the Berlin Christmas market attack as it was revealed the Polish driver of the hijacked lorry probably witnessed the carnage.

Lukasz Urban, 37, had driven to the German capital from Turin to deliver steel and had parked while he waited for his cargo to be unloaded but was ambushed as he returned to his truck from a kebab shop.

Mr Urban, a married father of one, appears to have been stabbed and beaten and police sources believe he was alive when the 25-tonne truck was steered at crowds on Monday night killing 12 and maiming 48.

The masked ISIS terrorist then shot him in the head before fleeing the scene. His escape was aided by police arresting the wrong man and giving him an 18-hour head start.

Detectives believe that piecing together what happened between the hijacking and the terror attack will lead them to their man.

Lukasz Urban (pictured), a 37-year-old father-of-one, saw his 25-tonne truck career through Berlin's Breitscheidplatz Square, which killed 12 and injured dozens more

Terror attack chain of events: The polish lorry was hijacked when it arrived in Berlin and hours later was driven through Christmas market crowds. The main suspect was pursued on foot and arrested - but it appears he is the wrong man. Police also raided the hangar he lives in with other asylum seekers at the Tempelhof airport

German newspaper Bild says a postmortem examination revealed Mr Urban was probably alive at the time of the terror attack and may have tried to grab the will. The source said: 'There must have been a fight.'

Police believe it possible that the mass assassin may have been trained as an HGV operator because it would, in the words of one investigator, 'been very hard for someone who didn't know what they were doing to drive an articulated truck through the streets of Berlin.'

Mr Urban was found dead in the cab and had been beaten, stabbed and shot.

Police used CCTV and GPS evidence from his truck to piece together his final hours.

The truck driver, from a small village in north-west Poland, was married with a teenage son. He arrived at steel firm ThyssenKrupp's depot in Friedrich-Krause-Ufer Strasse, four miles north of the Christmas market, at 8am local time on Monday.

But he was told there was no one to remove the load as he was a day early and he would have to wait until the next day.

It was not clear where he parked, but it is understood he stayed in the vicinity of the ThyssenKrupp's depot.

Brave: Owner of Polish haulage firm, Ariel Zurawski (left), insisted the driver Lukasz Urban (right) - also his cousin - was hijacked but tried to fight his killer

The boss, Ariel Zurawski, who is also the driver's cousin, said they last spoke at midday but the man's wife had been unable to reach him at 4pm - hours before the incident. Mr Zurawski is pictured above with wife Judyta

Mr Urban spoke to Ariel Zurawski, his cousin and boss, at around noon, when he said he was hungry. He visited a kebab restaurant in the area at around 2pm – where he was caught on CCTV – before returning to his cab.

His wife spoke to him at 3pm, when he complained about having to wait to get unloaded, but was never heard from again. At 3.19pm and 3.44pm the lorry's electronic systems recorded failed attempts to start the engine, followed by a series of 'erratic movements'.

Mr Urban's wife said she tried to contact him by phone at 4pm but could not reach him. The lorry was then driven in short distances towards the Christmas market.

During these short journeys the GPS showed that the engine appeared to be 'choking' so the company tried to contact the driver to find out what was happening. However, no one answered the calls.

Mr Zurawski said: 'It looks as if someone was trying to learn how to drive the lorry.' There was no more movement until around 7.34pm, when the truck started up again and travelled some six miles, sometimes turning in tight spots or crossing the double line, before arriving at the Christmas market.

Mr Urban's colleagues said his injuries showed he had 'fought to the end' to defend his vehicle.