A 10-year-old girl bludgeoned to death along with her mother in their Las Vegas home was sexually assaulted before she was killed, police said today.
Authorities have been working through a forensics "nightmare" in a house where police said there is blood in every room.
Officials discovered the deaths Monday after the young girl's 9-year-old brother told school officials that his mother and sister were dead at home.
Arturo Martinez, the girl's father,was taken from the home and is in critical condition at a hospital. His injuries were the result of "blunt force trauma," cops said.
Police have not yet been able to speak to him and said they are not calling him a suspect or ruling him out.
"We don't know if the father is a suspect or not," Las Vegas Metropolitan Police Officer Marcus Martin told ABCNews.com. "We have nothing to suggest that yet. We're not ruling anybody out."
Originally, authorities said the public had no reason to worry that a killer was on the loose.
"We don't have any evidence to support that there's somebody going around doing this," Martin told ABCNews.com on Tuesday.
But, today, when asked if if an outsider could be the perpetrator, Martin said, "We have not ruled that out."
Martin said authorities have doing "around-the-clock forensic work" since the bodies were discovered.
"Forensically, it's been a nightmare," he said. "It's been three days going through that house because there's no portion of the house that's not a crime scene. There's not a room without blood evidence in it."
He said there is a high volume of evidence, but could not go into details.
When officers arrived at the house on Monday, about a half mile from the Mabel Hoggard Elementary School that the boy attended, they discovered the bodies of the his 10-year-old sister and mother, Ignacia "Yarida" Martinez.
A 4-year-old sibling, who was distressed but unharmed, was also at the house, along with a wounded Arturo Martinez covered in blood.
Police are still trying to determine the timeline of events that took place.
The Las Vegas Coroner's Office determined that the cause of death for both mother and daughter was blunt force trauma. They specified that the mother suffered multiple blunt force head injuries from the assault and that her husband suffered similar injuries.
The 9-year-old boy who reported the deaths and his little brother have been taken into child protective services' custody. When asked if investigators have spoken to the boys to get a sense of what they saw, Martin said authorities are focusing on the boys' "mental health" after the trauma they have suffered.
"The last thing they need is investigators quizzing them," Martin said.