DENVER—A judge on Friday sentenced a former student to life in prison without parole for a 2019 shooting inside a suburban Denver high school that killed one teenager and injured eight others, telling the defendant he had shown no remorse and had failed to help a devastated community understand his actions. Devon Erickson, now 20, was convicted in June of 46 charges, including first-degree murder in the death of Kendrick Castillo, an 18-year-old senior hailed as a hero for trying to stop the attack on a classroom at STEM School Highlands Ranch, south of Denver. Prosecutors said Erickson partnered with fellow student Alec McKinney in the May 7, 2019, shooting. McKinney told investigators that he planned the attack for weeks and intended to target classmates who repeatedly mocked him because he was transgender, according to court documents. Since Erickson was 18 at the time of the attack, he faced a …