SPRINGTOWN (CBSDFW.COM) – A newborn suffered a traumatic brain injury at the hands of his mother’s 20-year-old boyfriend, according to the arrest affidavit.

Authorities have charged Kaleb Eisenmann, 20, with Injury to a Child.

Kaleb Eisenmann (photo credit: Parker County PD)

The infant is fighting for his life at Cook Children’s Hospital, where he arrived with hemorrhaging in the brain and bruises on his body. He suffered at least one seizure since his injury and is in the intensive care neo-natal unit.

A Parker County sheriff said Eisenmann was watching the 8-week-old boy, a 2-year-old and a 6-year-old while their mother was at work.

Eisenmann implicated himself, saying he was “frustrated” and that he jerked the baby up out of an infant swing too hard enough to “maybe cause injury.” Eisenmann said that caused the infant’s “head to jerk back.”

“I didn’t slam him in the bed,” Eisenmann told investigators. “But I put him down really kinda hard[sic],” according to the Sheriff’s Office.

The case is still under investigation.