Clifford Helmka, 18, faces charges after police say he shook the infant.

Howard County Prosecutor Mason Gebhardt says this case is tugging at his heart.

"Of course, I hope it goes without saying that our thoughts and our prayers are with the family at this very difficult time," Gebhardt said.

The prosecutor announced the new charge -- murder in the second degree -- against Helmka in the death of his girlfriend's daughter Jocelyn. The girl died Tuesday.

Police say Helmka was watching the infant last week while her mother was away at work. Police say Helmka admits shaking the baby for two or three seconds in an attempt to quiet her crying.

Howard County Sheriff Charlie Polson said the death has rocked the close-knit community of Glasgow.

"It's a small community. People know everybody and know the family and the victims and so forth. So it's pretty hard and pretty traumatic on a small community like that," Polson said.

A friend of baby Jocelyn's mother said she's holding up as best as she can.

If convicted, Helmka faces 10 to 30 years in prison. Helmka is in jail on $250,000 bond. He faces arraignment July 17 in Howard County Circuit Court.