Police in Kentucky have arrested one person and are looking for a second suspect in a toddler abuse case that prosecutors and investigators say is the worst case they’ve seen in someone so young.

Seventeen-month-old Elena was presented at Middlesboro ARH Hospital on July 28 with injuries so severe that she was almost immediately flown to East Tennessee Children’s Hospital in Knoxville, WBIR reported.

The little girl died Sunday night, police said. Her mother, 21-year-old Erica Lawson, was arrested and charged with manslaughter, failure to report child abuse, criminal abuse, and wanton endangerment, according to WVLT.

“This is one of the most severe cases of abuse, specifically because the baby was 17 months old,” Commonwealth’s Attorney Lisa Fugate said.

At a vigil on Tuesday, Fugate promised to seek the most severe penalty she could. “If I can seek the death penalty, you better believe I will,” she said.

Prosecutors have said the baby girl was sexually abused. Meanwhile, detectives said they have been tracking down hundreds of leads in their search for the second suspect and have collected DNA from many of the people they’ve interviewed and sent it off for analysis.

“That somebody could be that sick out there to let this go on,” Middlesboro Police investigator Caleb Ayers told WBIR. “I have seen some kids like that, but not at this age.”

Ayers said the mother could face more charges.

“The mother and father were not together. The father is not a suspect at this time, but that could change,” he said.

Middlesboro Police Chief Petie Gilbert told WVLT that a family member reported the abuse in early July.

“There was a report made earlier. The uncle contacted us, and we could never find the kid. The uncle did not know where the kid was at the time,” Gilbert said.

Police said Lawson was being held on a $1 million bond and was due in court on August 8.

Friends and family were holding another vigil Saturday night.

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[Featured image: Baby Elena/handout]