Illustration of the mechanism to reach a planetesimal population with high orbits, as explored in this paper. a) both the planet orbit (dotted) and planetesimal orbits (solid) start out in the orbital plane. b) As the planet has migrated in a some distance, the planetesimals are stuck in an MMR. As they are dragged along their orbits become increasingly eccentric. c) At some point the planetesimal orbits become so eccentric, the bodies become planet-crossing. As the eccentricity rises even further, the relative velocity between the planet and the planetesimals grows. d) The high relative velocity compared to the local Keplerian velocity enables the planet to violently scatter the planetesimals throughout the system, to orbits with high inclinations.