Bystander assists cop when knife search turns into struggle

Suspect attempts to flee when a police officer searches him. As the struggle begins, a large knife can be seen tucked in to the rear of his belt. The knife falls to the ground as he escapes the grip of the cop. As the cop again grabs the suspect and pulls him to the ground, a bystander who apparently has some training in grappling assists by controlling the legs of the suspect. The bystander then transitions to a rear naked choke which effectively restrains the suspect who stops resisting.

Slam while applying submission from ground

MMA fighter attempts triangle choke from bottom ground position. His opponent raises and slams him into the floor, resulting in a knockout. This is exceptionally dangerous and would most likely result in death on a hard surface.

This can be avoided by using techniques which break the posture of the person attempting the slam and bring them back to the ground, or by abandoning the technique as below. The slam is attempted by the same MMA fighter as the above video: