Police say a Bronx man was arrested for physically abusing his 4-year-old stepson.

The family lives on Vyse Avenue in West Farms.

Police say 28-year-old Trevor Brown punched the young boy in the stomach around 7:30 p.m. Monday, seriously injuring the child. According to a New York Daily News report, Brown allegedly punched the boy to keep him away from his 11-month-old brother.

The paper reports that the mother left to buy juice and noticed blood and bruising on the 4-year-old when she returned 15 minutes later. She was the one who called 911.

The 4-year-old is expected to be OK.

Brown is facing charges of harassment, second-degree assault on a person under 11 years old and acting in a manner injurious to a child.

The city Administration for Children's Services released a statement to News 12 saying, "ACS and NYPD are actively investigating the circumstances leading to this incident involving a minor. Confidentiality laws preclude us to comment further."