Why do you think Leon and Ken do not tell Father Paul about Teofilo's death right away

because they killed him

Because they did not want Christian interference in the burial of Teofilo.

Explanation:

The short story "The Man To Send Rain Clouds" is written by Leslie Marmon Silko. The protagonist of the story is Teofilo, a shepherd who died while tending the sheep.

When Leon and Ken arrive at the place where Teofilo was lying dead under a tree in the pasture they perform the burial rituals. While taking back the corpse of Teofilo back to home, they met Father Paul who asks them if they found Teofilo or not. Len and Ken did not tell Father Paul about his death because they did not Father Paul to interfere in the burial rituals of their grandfather according to Christian rituals.