Police continue to investigate a shooting that left a family dead.

It happened Tuesday at a home near 47th Avenue and Cactus Road.

According to Phoenix police, Alex Buckner, 26, opened fire inside his home, shooting his parents and two sisters, before setting the house on fire.

Buckner was shot and killed after a confrontation with officers.

[READ: PD: Man kills parents and sisters in Phoenix home]

[SLIDESHOW: Gunshots inside home on fire]

One of the big questions now is why. How could someone suddenly decide to murder his entire family?

Buckner's aunt said that he suffered from schizophrenia. She said that this is not a story of dysfunction but tragedy.

Police and fire investigators were out at the home Wednesday morning, sifting through evidence.

People who knew the family said 18-year-old Kaitlin was bright, responsible, kind and a freshman at Gateway College with her whole future ahead of her. Her younger sister, 6-year-old Emma, was a charming and smart first-grader. Their father, 50-year-old Vic, worked in construction. Their mother, 49-year-old Kim, worked in the office at Greenway High School. Students say she was a sweet lady.

"She was really friendly, she was the assistant secretary at Greenway so if you ever had a problem, you would go to her," student Anna Lenz said. "She was really nice."

"She was very nice, she would always greet everybody with a smile, whatever you were in there for, she made it better," said Greenway student David Suvia.

Police said Buckner had previous run-ins with the law. He was arrested twice just outside Tulsa, Oklahoma, for drug-related charges and the other for shoplifting.

Family members said he was no longer using drugs when the shooting happened.

Copyright 2016 KPHO/KTVK (KPHO Broadcasting Corporation). All rights reserved.

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