The El Paso Times reports that Luis Javier Solis Gonzalez is charged with capital murder in connection with the May deaths of 34-year-old Marysol Saldivar, 42-year-old Eric De Santiago and 13-year-old Cassaundra Holt.
Prosecutors have already filed a notice of intent to seek the death penalty.
An indictment says Solis Gonzalez strangled the girl, struck her mother on the head and stabbed De Santiago.
According to police, Solis Gonzalez and Saldivar's 4-year-old son saw the attack.
Solis Gonzalez's attorney tells the newspaper that he's disappointed by the prosecutors' decision.