You were on a mission with Ghost, shooting at the enemy when you ran out of bullets so you had to choose another strategy.

You remember you had knives in your bag, you took them out.

One of the enemy launches towards you, you take a notice of that and aim a knife and throw it at the enemy, to celebrate you do a little dance then you crouched down and stabbed the enemy in their soft spot, causing them to black out completely.

You notice Ghost, he saw everything and he was proud of his girl.