Autopsy results on Kaitlin and Ethan Austin were released Thursday, three days after they were found dead at their Hansen Park home in Kennewick.
Kaitlin, 16, died from multiple gunshot wounds to the head and body, according to Benton County Coroner John Hansens. Officials would not say how many times she was shot.
Her stepbrother, Ethan, 12, died from a single gunshot wound to the head, Hansens said. Officials would not say whether it was self-inflicted.
Police told the Herald it's too early to label the deaths a murder-suicide, saying they need to wait on the results of forensic tests to try to determine what happened at the house on West Third Avenue.
There is no evidence so far to indicate someone else killed the children, that the shooting was an accident or that anyone else was in the house when it took place, said Ken Lattin, Kennewick police spokesman.
"It's important that the community know there are no suspects, no persons of interest and no one else out there," Lattin said. "There is no indication that there is anyone else involved in this other than these two kids. Why it happened we don't know."
Andrew Austin, stepfather of Kaitlin and father of Ethan, found the children about 5 p.m. Monday inside Kaitlin's bedroom, Lattin said. A handgun found near the bodies is being tested to see if it was used in the shooting. Andrew Austin told police the gun belongs to him.
Police would not say how many bullets were fired inside the house or what caliber handgun was found.
There were other guns in the home that were legally registered to Andrew Austin, Lattin said. He declined to say what type or how many. Investigators are looking into whether either child had any weapons training.
The Austin family has been cooperative, Lattin said. Detectives met with family members to go over the investigation and autopsy results before they were released to the media.
Investigators plan to talk more with the Austin family and close friends of the children to try to shed some light on the circumstances surrounding the shootings, Lattin said.
There is no clear motive, Lattin said. There was no note at the scene or anything to indicate the shooting was planned.
Police have not found anything unusual about the relationship between Kaitlin and Ethan, Lattin said. A search of their social media accounts and cellphones hasn't revealed any rifts or suspicious activity. As far as investigators can tell, the children seemed "pretty normal."
Kaitlin was a pitcher on Kamiakin High School's softball team, which has won three consecutive state titles. Her friends said she was an intense competitor who loved to make people laugh off the field. She was known for an infectious smile, goofy personality and ability to make anyone feel welcome.
Ethan was a Boy Scout and sixth-grader at Desert Hills Middle School. Friends called him a leader who liked to build fires, be outdoors and play golf.
Police are doing their best to learn more about the siblings' relationship and what may have led to them ending up dead, Lattin said.
"Right now we don't have any indication of any issues, but again it's still ongoing and more could develop there," Lattin said. "There have been no red flags that have been revealed."
The forensic testing is expected to take weeks and it could be a while before police are able to provide more details on the shooting, Lattin said.
The main goal of the department moving forward is to try to provide some answers to a community shaken by the shooting and some peace of mind to the Austin family, Lattin said.
"This is unusual. Something happened to trigger all of this and we don't know what at this point," he said. "But it's far from over. This is still important for this family to know what happened and we are going to do our best to get those questions answered for them."