Updated

An Arkansas man has been charged with two counts of first-degree murder following the deaths of two infants in separate incidents.

Springdale police said Thursday that Travis Fox admitted to investigators that he "violently shook" his 7-month-old son, who was pronounced dead at a hospital on Wednesday.

Police in West Fork and the Washington County Sheriff's Department say Fox was already under investigation for the Sept. 4, 2011, death of another of his children, who was 6 months old.

Springdale police arrested Fox for the 7-month-old's death and Washington County deputies charged him in the 2011 death.

The sheriff's office says Fox also admitted shaking the younger of the babies.

It was unclear whether Fox had an attorney. He was being held Thursday without bond.