Police in Baltimore have arrested a 14-year-old boy who told them he beat his grandmother with a hammer.

Police spokeswoman detective Nicole Monroe says the boy called 911 after the Thursday morning assault.

The 66-year-old woman was taken to a hospital, where she was listed in critical condition.

Monroe says that in an interview with detectives, the boy said he hit his grandmother multiple times after got angry while getting ready for school.

The teen was being held by authorities but he wasn’t identified because he hadn’t been formally charged as of late Thursday.

It wasn’t clear if the boy would be charged as an adult. Fourteen is the minimum age in Maryland that someone can be charged as an adult.