They might've killed her because of her skin colour. They might've done it because they were cowards who entered the wrong line of work and were shitting their pants at the sight of a female with a knife. Or they might've been too low IQ to get one officer to distract her or even taze her while another came at her from behind and subdued her, after which they could have both easily disarmed her and placed her on the ground for arrest. Or it might have been some combination of two or all three of these reasons.
Just lol at Somalis expecting BLM support.