R OCHESTER HILLS, Mich. — Kira Pennock said her friend, Jennifer Crumbley, sent her a text message in the aftermath of a Nov. 30 shooting rampage at Oxford High School, telling her “my son ruined so many lives today.” The comments came hours after Pennock said Crumbley, the mother of 15-year-old Ethan Crumbley, had sent her a screenshot of a troubling drawing Crumbley’s son was caught drawing on a math assignment. Crumbley told Pennock, the 25-year-old owner of a Metamora horse farm, that morning that she’d had a “s— day,” and “just had to go to my son’s school and meet his counselor.” “I wa…