SAN ANTONIO - A doctor said a four-month-old boy has a devastating brain injury because of being shaken violently by his babysitter.

Tomasa Mercedez Guerra faces a charge of injury to a child San Antonio, according to police.

An arrest warrant said the victim was taken to University Hospital on April 27 for falling off a couch onto a carpeted floor. Police said Guerra, the child's sitter, found the injured baby.

Investigators said the child's injuries did not match Guerra's story.

In fact, during the victim's initial examination the doctor noted the improbability of a child so young rolling over a couch and an entire row of pillows.

A warrant said Guerra's story was filled with holes. She claimed the baby landed on a concrete floor when the area in question is carpeted.

The 31-year-old eventually told detectives she shook the infant in a playful manner, police said. The arrest document said she did not think it was going to harm the boy.

According to the warrant, the child's injury was nearly fatal.