How did hrothgar know ecgtheowbeowulf's father?

On page 33 of Seamus Heaney's bilingual edition of "Beowulf", the narrator explains that Hrothgar paid a debt on behalf of Beowulf's father, Ecgtheow. Ecgtheow began a feud after killing a Wulfing. This provoked fear among the Geats, Ecgtheow's people, and they forced him to leave. So he ran away to the land of the South-Danes, Hrothgar's kingdom. Hrothgar was meanwhile "in the first flush of kingship". Hrothgar assuaged the matter by shipping a treasure-trove to the Wulfings. After this, Ecgtheow paid Hrothgar his allegiance.