article_snippet: The two attackers encounter a man with a backpack walking down a flight of stairs in the museum - but let a visitor escape with a third man life before carrying out the attack .
article_snippet: a third man man in the backpack scuttles off as the two armed men prepare to carry out the attack .
article_snippet: One of The two attackers  is wearing a baseball cap and a heavy jacket, while the other wears a red hooded jumper and tracksuit pants.
article_snippet: At one point, they encounter another man with a backpack walking down a flight of stairs.