Maria LaGuerta died in Dexter due to a gunshot wound. She was investigating Dexter as the Bay Harbor Butcher and came very close to exposing him. Dexter planned to kill both Maria and a drug kingpin, Estrada, and make it look like they killed each other. However, when Maria was incapacitated and Dexter was about to kill her, Debra, Dexter's sister, arrived and instead of letting Dexter kill Maria, she shot and killed Maria to protect Dexter's secret.
