It has been six months since 2-year-old Koltyn Sparks died of blunt trauma, and Sonora Police Chief Turu VanderWeil said Thursday his investigators are reinterviewing the people who last saw him and collecting more evidence.

The case is considered a suspicious death, and VanderWeil said he’s not ready to call it a homicide.

Koltyn’s great-aunt Teresa Blackwood said the family understands the challenges the police face but they are frustrated at the length of time the case has taken.

“I’m here in this town looking over my shoulder for the person who killed my nephew,” she said.

VanderWeil said the investigation got off to a tough start because of a delay in his agency being notified that a child in Sonora had died under suspicious circumstances.

Koltyn was being cared for in a Shepherd Street home while his mother Nicole Sparks worked. She and the caregiver took Koltyn to the emergency room at Adventist Health Sonora, where doctors transferred him by air ambulance to University of California Davis Children’s Hospital.

Adventist Health did not call the police about a case of suspected child abuse.

When Koltyn died on Jan. 15, investigators from Stanislaus County Sheriff’s Office took over the case because that is where Koltyn lived with his mother. That’s when Sonora Police were brought in.

VanderWeil said he’s working with the Sonora hospital to review their policy on notification in such cases.

Karen O’Brien, communications manager at Adventist Health Sonora said she could not comment on this particular case but the hospital has aggressive policies on reporting child abuse.

“We work closely with law enforcement and Child Protective Services,” she said.

He said another complication has been that investigators have been working with reams of medical information from the hospital and the coroner’s report from Stanislaus County.

Koltyn’s paternal grandmother Tracy Gulcynski said medical records from UC Davis showed Koltyn suffered blunt force trauma to the abdomen, which was cited as the cause of death, oxygen deprivation, brain damage, severe dehydration. There was evidence he had been shaken.

VanderWiel declined to give out any more information to protect the integrity of the investigation.

“Knowledgeable information released too soon about particular facts could change the outcome of the investigation based on how it could be used by suspects, witnesses,” he said.

District Attorney Laura Krieg said she has assigned to the case Harold Nutt, a recently retired Deputy District Attorney in Merced County. He is working with investigators to build the case.

“We always get involved early on,” Krieg said.

Nutt is joining the DA’s office for two years on a part-time basis to comply with the rules of the California Public Employees’ Retirement System.

VanderWeil said he understands the frustration the family feels.

“I would feel the same way,” he said. “I know it’s been a long time but we have to be really careful not to put the wrong person in jail. It’s not as clear cut as it looks. We have a lot of work to do.”