An eye-witness account describing the final moments of the fearsome German flyer known as the Red Baron has emerged for sale nearly 100 years later.

And the description of the shooting down of Manfred von Richthofen's famous red tri-plane towards the end of the First World War could solve once and for all the mystery over who did kill the 'ace of aces'.

The brilliant pilot, who was credited with a staggering 80 kills in the war, was shot down as he chased a British Sopwith Camel plane over the River Somme near Amiens in France at just 400ft from the ground.

A document, right, outlining the final few moments of feared German First World War ace Manfred von Richthofen, left, has emerged and is being auctioned by Bonhams in New York on Wednesday

The Red Baron's aircraft, pictured, was shot down near the Somme in 1918 after he was ambushed

Among the items going for sale on Wednesday is this Balkan Cross which was taken from one the Red Baron's earlier aircraft and is expected to reach in the region of £80,000 when it goes under the hammer in New York

As the planes neared the Allied lines, bursts of fire from a second Allied plane, a machine gun and two Lewis light-machine guns on the ground opened up at the Red Baron's aircraft.

The account now for sale from Lieutenant Donald Fraser describes how von Richthofen's plane was 'wobbly and irregular' immediately after the machine gun operated by Sgt Cedric Popkin opened up on him.

The German plane crash landed and the pilot was found to be dead having been shot through the chest.

Canadian pilot Captain Roy Brown was officially credited by the RAF with the coveted 'kill' after pursuing the German upon seeing a comrade in the Sopwith being tailed by him.

In 2002 two separate TV documentaries - one by Channel 4 and the other by the Discovery Channel - claimed Popkin and Lewis gunner Willy Evans respectively had fired the fatal shot.

But Fraser's typed account states: 'I congratulated Sergeant Popkin on his successful shoot but afterwards found out that two A.A Lewis Guns...had also fired at this plane when it was directly over my head.

'(They) probably assisted in sealing the fate of this airman as he apparently flew right into their lines of fire. However, I am strongly of opinion that he was first hit by Sergeant Popkin's shooting as he was unsteady from the moment of that first burst of fire.'

Some photographs of the aftermath of the Red Baron's demise are also being sold in Wednesday's auction

Among the items for sale this week is a fabric fragment from the Red Baron's plane, top left

As well as the document, several photographs taken by Fraser of the wreckage of the Red Baron's Fokker plane and one of him stood at the German flyer's grave are also for sale.

Also at auction is a large section of aircraft skin featuring a black Balkan cross taken from a previous plane flown by von Richthofen. The 34ins by 22ins framed section of fabric is valued at £80,000 alone.

The pictures and Lt Fraser's eye-witness account were acquired years ago by an aviation historian who is now selling them for an estimated £5,000.

Tom Lamb said: 'Trench warfare in World War One was terrible and dire and claimed thousands of lives. Nobody wanted to read or know about that after four years of it.

Lieutenant Donald Fraser, pictured here standing by the Red Baron's grave, wrote the account of his death

The Red Baron died in his distinctive Fokker triplane, pictured, when he was shot down over France in 1918

'Then along came this dashing pilot of the air and he was a bit of a breath of fresh air, even though he was the enemy.

'He quickly gained a reputation as being a great pilot and a hero of Germany.

'All the Allies tried to get him. At one stage the British formed a squadron to specially to hunt down Richthofen and offered large rewards and an automatic Victoria Cross to any Allied pilot who shot him down.

'There has been a lot of controversy as to who did indeed shoot him down and this document is a fairly strong piece of evidence to support the case of Cedric Popkin.

'But in the scheme of things, does it really matter who shot him down?

'This impressive collection relating to the Red Baron reflects the mystique and legendary reputation acquired by the German flying ace which has endured long past his death in battle at the age of 25.'

Mr Lamb said that the piece of aircraft skin, that measures 34ins by 22ins, was a reciprocal gift from von Richthofen's widow to a Colonel Kimbrough Brown who presented her with a copy of his 1964 book, 'Von Richthofen and the Flying Circus'.

Col Brown's family sold it to a private collector over 25 years ago and the collector is now selling it.