Police arrested a Kingsessing man on assault charges last night after he allegedly beat and burned his girlfriend's 3-year-old son.

Matthew Montgomery, 27, of Conestoga Street near Woodland Avenue, was watching the toddler while his girlfriend was at work when the injuries occurred shortly after 7 p.m., said Officer Leeloni Palmiero, a police spokeswoman. Paramedics rushed the boy to Children's Hospital of Philadelphia, where doctors found that he had severe burns to his face, shoulder and back, swollen hands and legs, multiple bruises around his body and a concussion, Palmiero said.

Montgomery initially told hospital staff that the child had fallen from a slide at the park and then got burned when Montgomery used a rag he'd dipped into a stovetop pot of hot water to wipe down the boy, Palmiero said. When nurses questioned his account, Montgomery then told them the burns occurred when he used alcohol and peroxide on the boy's injuries, Palmiero said. He then wrote a letter of apology and admitted he hit the child in the head and beat him with a shoe, she added.

"What he said is obviously not consistent, so they're still investigating and sorting out what happened," Palmiero said.

Montgomery, who court records show has two prior drug and gun convictions, is charged with aggravated assault, simple assault, endangering the welfare of a child, possession of an instrument of crime and reckless endangerment, Palmiero said.

The boy remains in stable condition at Children's Hospital.