Buffalo (WBEN) -- The Buffalo police officer who used his weapon to shoot and kill a knife-wielding woman on Wednesday was justified, says Police Commissioner Daniel Derenda. 

Derenda spoke with reporters outside Buffalo City Hall on Thursday morning. 

Veteran police officer Robert Yates is now on administrative leave after using his gun to shoot and kill Charlene Fears, 38, who had threated officers with two large knives. 

"We believe the officers were justified in the use of deadly physical force," Derenda said.  

Fears also stabbed her young grandson, Roderick Geiger III, 4, who some neighbors knew as "Manny," police say.  The child eventually died at Women and Children's Hospital on Wednesday night.

Derenda was also asked about Fears' mental state, but he could comment on that as of now.

"Again, right now, everything is under investigation. I can't comment further at this point," he said.

Police say the officers were on routine patrol in the Riverside section of the city on Wednesday, when they got flagged down about the bleeding child.  At some point, Fears threatened the officers with the knives, leading to the officer shooting.