An easy way to do this is while going for the "It's A Trap!" achievement with a boosting partner.
Play as counselor and find a bear trap. Place it and let your boosting partner walk into it as Jason. You can use the same bear trap over and over again until Jason goes into Rage-Mode.
Hit Jason with a machete and he should lose the mask.
Simply grab it and your achievement will unlock.
Edit: Thx to "Mister Buds" for the machete-info in the comments!