BOSTON (CBS) -- An 18-year-old woman is undergoing a psychological evaluation after Boston police say she slashed a 4-year-old boy with a box cutter.

Police were called to a home on Paris Street after hearing that a child was in danger.

Witnesses were able to wrestle the boy away from the woman, and he was treated for non-life-threatening injuries at a hospital.

The suspect locked herself in a bedroom, and police had to use a battering ram to get through the door. Officers fired a less-lethal shotgun at her hand after she refused to drop the knife, and took her into a custody after a "brief but violent struggle," police said.

"The actions of the officers and the assistance of the witnesses undoubtedly saved this young child's life," Boston police said in a statement.

The woman is expected to face several criminal charges.