ALBUQUERQUE, N.M. (AP) — A state worker at a residential treatment center for juveniles on Wednesday described the New Mexico teenager who shot and killed five family members in 2013 as having matured into a role model for other troubled boys at the facility.

Meanwhile, one of 18-year-old Nehemiah Griego's teachers said he was a good student but had expressed racist viewpoints and a fascination with history, war and Nazi Germany.

The testimony from staff at the state-run Sequoyah Adolescent Treatment Center in Albuquerque came during the third day of a hearing that will determine whether Griego should be sentenced as a juvenile or an adult for killing his parents and three younger siblings.

Griego was 15 when he opened fire in his family's home south of Albuquerque in January 2013, killing his mother as she slept, then his younger brother and two sisters, authorities said. Griego's father was the last of the five to be killed, with sheriff's officials saying he was ambushed by his teenage son after he returned home.

"There were times that he cried," said Armando Heras, who supervises Griego and other teens at the treatment center, when asked about Griego's demeanor at the facility. "I assumed he was crying because he missed his family."

Griego pleaded guilty in October to two counts of second-degree murder and three counts of child abuse resulting in death.

Several witnesses for both the prosecutors and the defense have said the teen was physically abused by his father, a former pastor at an Albuquerque megachurch and Army veteran who had trained his son to use firearms and tasked him with guarding the family's home.

At least once, Griego was beaten so severely he lost consciousness and likely has suffered traumatic brain injury from the abuse, public defender Stephen Taylor said.

In court on Wednesday, Heras testified that Griego arrived at the facility with an intensely quiet and reserved personality, but he eventually began to open up, socialize with others and carry himself as a leader.

"It was hard to get him to talk about his problems and what he was thinking about," Heras said, when asked about Griego's demeanor when he first arrived.

Prosecutors have focused largely when questioning witnesses on Griego's manner immediately after the shooting and during psychological examinations, with those on the stand suggesting his demeanor seemed emotionless and even callous in light of the tragedy.

In court, Griego has shown little emotion, except for an instance on Tuesday when he wiped his eyes as an investigator described the crime scene the night authorities discovered the five family members' bodies.

Griego apparently referred to the family home during conversations with Heras as "the fort," the treatment supervisor said. Griego has been at the center for 20 months, more than twice as long as any other boy currently undergoing treatment there.

A judge must decide, based on testimony during court proceedings this week and in February, whether Griego can be rehabilitated through treatment at the state facility that aims to prepare violent juvenile for reintegration into society.

Griego's sentencing terms could range from probation to three life sentences plus 30 years if he is sentenced as an adult, his attorneys said. If he is sentenced as a juvenile, he would theoretically remain in the custody of the state Children, Youth and Families Department until he is 21.