A grand jury has indicted a 22-year-old Idaho man on murder charges in the deaths of three people last month at a Boise home.

Adam Michael Dees of Nampa is charged with three counts of first degree murder, robbery and other crimes.

Prosecutors say they believe Dees killed Theodore M. Welp, 80; his wife, Delores Elaine Welp, 77; and their son, Thomas P. Welp, 52, on March 8 or 9. All three victims were shot in the head and beaten with a baseball bat, according to the indictment. Thomas Welp was also stabbed in the neck, the indictment says.

Ada County Prosecutor Jan Bennetts has 60 days to decide whether to pursue the death penalty in the case.

Bennetts and Sheriff Gary Raney announced the indictment at a news conference Wednesday afternoon. Dees has been in jail since March 11, when he was arrested and charged with grand theft and other crimes after law enforcement officers said he was found with credit cards linked to the Welp family.

Bennetts declined to provide additional details about the killings, saying those answers needed to come out through the court process to ensure Dees gets a fair trial.

According to court records, Dees has been assigned an attorney from the Ada County public defender's office, but the office was closed Wednesday evening. The Associated Press could not immediately reach Dees' public defender for comment.

Dees has not yet had an opportunity to enter a plea or appear in court on the new charges.

The sheriff, Gary Raney, said 50 detectives, crime-scene investigators and deputies have logged more than 1,000 hours working on the case during the past four weeks.

The Welps formerly lived in Arizona, where Theodore Welp was the chief of Tucson Electric Power Co. in the 1980s.