(NewsNation) — A father of four children was out Christmas shopping when a fire broke out, killing all the children in the home.

Police in Bullhead City, Arizona, said it is continuing the investigation into the fatal fire on Saturday night. Five children were at home; a 13-year-old boy, a five-year-old boy, a four-year-old girl and a two-year-old boy who lived there as well as an 11-year-old boy who was visiting.

The children’s father told investigators he was gone for about two and a half hours, buying Christmas gifts and groceries.

Initial investigations suggest the fire began in the downstairs foyer area before traveling up the only staircase, making it impossible for the children to escape.

Emergency responders received a call at 4:45 p.m. and firefighters arrived on scene five minutes later, with the fire extinguished by 5:03 p.m. Neighbors reportedly tried to rescue the children, including using a ladder to try to reach the upstairs bedroom where all the children were found.

Investigators from a different department and the Bureau of Alcohol, Tobacco and Firearms were called to assist in the investigation because the children’s grandfather is an employee with the Bullhead City Fire Department.

Investigators are still working to figure out how the fire began. Names of the victims are being withheld pending an official identification.

Authorities are asking anyone who may have photos or video to call (928) 763-9200 and ask to speak with detectives.