Harry Potter and the Prisoner of Azkaban (Harry Potter, #3)

by J.K. Rowling

“Harry . . . I as good as killed them,” he croaked. “I persuaded Lily and James to change to Peter at the last moment, persuaded them to use him as Secret-Keeper instead of me. . . . I’m to blame, I know it. . .

but like why did he do that??