Old Prussians
It is true that in 1237 the entire right bank of the lower Vistula was occupied by Old Prussians and that Truso was in or projected into the Old Prussian dukedom of Pomesania. Moreover, Adalbert of Prague, who came with Boleslaw Chrobrie's soldiers, had been beheaded further north-east at the coast of the Baltic Sea near (Fischhausen), now Rybaki, for cutting down the sacred groves of the Old Prussians as part of an effort to conquer them under guise to convert them in (997 AD). This circumstantial evidence is not conclusive about the ethnicity of the founders of Truso.