You'll Be the Death of Me by Karen M. McManus

Ivy, Mateo, and Cal—three former close friends from middle school—decide to ditch school for old times' sake on a day when each of them desperately needs an escape. Their impulsive plan takes a deadly turn when they spot another classmate, Brian "Boney" Mahoney, also skipping school and decide to follow him . They inadvertently walk into the scene of his murder, making them potential witnesses—and suspects .

As the three try to piece together what happened to clear their names, they discover they all have a secret connection to the dead boy. Forced to confront their own hidden truths, Ivy, Mateo, and Cal must work together to find a killer before their chance reunion becomes their last