Police say two young sisters were killed Thursday by their 20-year-old half-brother in West Deptford.

Authorities say Marqueese Lee struck Lucille Bevan, the girls? mother, on the head with a hammer. Investigators say Bevan was able to flee the home with a 1-year-old child, but the two sisters were left inside.

When authorities arrived, officials say Lee held a knife to his chest, keeping them out of the home for about 90 minutes. Police say they found 6-year-old India Duncan and 10-year-old Aliah Scott dead after they were able to take Lee into custody.

Autopsy results revealed the two girls were strangled. Crisis counselors met at the Oakview School, where Scott was a fourth-grader, to prepare for students on Monday.

Lee has been charged with aggravated assault on Bevan. He is undergoing psychiatric evaluation and is being held on $750,000 bail.