Sonora Police Chief Turu VanderWiel said Tuesday a 22-month-old boy who died in January died of blunt injuries.

“We must maintain the integrity of this investigation, so we cannot release any further details,” he said in an email. “Our investigation will be focused on finding out what happened.”

Koltyn Sparks was admitted to Adventist Health Sonora in January for flu symptoms but was found to have severe brain and internal organ damage. He was unresponsive when he was airlifted to University of California Davis Children’s Hospital early in the morning of Jan. 15 and died that afternoon.

His paternal grandmother Tracy Gulcynski said Tuesday that learning the cause of death was bittersweet.

She said the injuries were to his abdomen.

“We had confirmation of what we suspected all along,” she said. “It’s very heartbreaking but we look forward to the investigation and the arrest.”

She said she’s been told authorities are bringing in a forensic specialist to go over the evidence and create a better timeline of where Koltyn was and who he was with.

The boy had been staying with someone on Shepherd Street in Sonora while his mother worked and that person took him to Adventist Health. He lived with his mother in Waterford in Stanislaus County.

That’s why the coroner there began the investigation after a report from UC Davis showed Koltyn was severely dehydrated and had been deprived of oxygen, possibly smothered and had been shaken.

VanderWiel received the Stanislaus County coroner’s report Monday.

VanderWiel said last week investigators had talked to the mother and the person Koltyn was staying with.

Gulcynski’s son Josh Blackwood had not seen his son in more than a week when Koltyn died.

Gulcynski said the family has been uplifted by the many people who have reached out to them since they took their story to the media and created a Facebook page “Justice for Koltyn.”

“People from Canada, Washington, Montana, not to mention our own communities, Oakdale, Modesto, Sonora, Jamestown.”

They did so because authorities did not release information that Koltyn had died and the coroner’s report had taken more than 100 days to be released.

“There are certain stages of grief,” she said. “We’ve hit that stage where we’re angry. We’re going to stand up for him. We want justice. We want something done.”