"This is a complete tragedy," Spangler said. "We're not ruling anything out. We can't rule anything in at this point. Nothing is stepping out to us to say that there is some predator out there ... we just don't know yet."
Early Thursday, police feared the boy endured some kind of physical attack at the Not Your Ordinary School campus of pre-kindergarten through third grade.
By late afternoon, police said the hook was low enough that the boy might have gotten himself stuck.
"It was not impossible for him to have gotten up there by himself," Spangler said, declining to say how high the hook is on the wall or how tall the victim is.
Police have not ruled out assault, Spangler said.
"We don't know how he got up there," he said.
Spangler also confirmed that the boy's pants were down around his ankles when he was found, but investigators believe they fell while he was suspended and have no evidence of sexual abuse.
At an earlier news conference, Lt. Jeff Hampton of the Austin police child abuse unit said the scene was considered "suspicious" and that investigators were focused on questioning students.
Whether criminal charges could result remains unclear. If another student is found to have been involved, state criminal laws don't apply to children under 10, said LaRu Woody, Travis County assistant prosecutor.
The boy attended an assembly Wednesday but asked to be excused to go to the bathroom. He was found by a male teacher as the assembly was breaking up.
There is no surveillance camera video and it was unclear how long the boy was on the hook. Police said they were hampered in their immediate investigation because school was being let out for the day and the students were leaving campus.
Spangler said they don't have any evidence the boy had been bullied in school.
A telephone message left for school administrators seeking comment was not immediately returned. A message on the school Web site said staff is cooperating with the investigation.
"The safety of our students is our first priority. As information regarding this incident comes to light, we will determine what, if any, campus safety issues need to be addressed," the school said.
The school earned an exemplary rating, the highest possible, from the state for the 2006-2007 school year.
