You will be provided with the rule  below that clearly states that he does not have to comply to your demands because he was already holding a big weapon first. 
A jack hammer is the same class as a RPG or any other big weapons.  Thats why they fall under the big weapon class. 

2.8 FearRP - If you are at gunpoint and you weren't holding a gun first (melee weapons aren't classed as guns), you must (within reason) follow their demands. You can't pull out a gun from your hotbar, or equally, equip one from your inventory. Do not do anything that would risk your life under FearRP. The side with most armed people would be in charge of the situation. For example, a gang of 3 could stop one guy even if he has a gun. FearRP ends after the first shot is fired.

You must use /me to conduct FearRP. For example: '/me handcuffs [name]' or '/me locks vehicle door' to prevent escape.

- Taking hostage: Once you are under their control, you must comply until someone pays your ransom, breaks you out or if the owner dies. The police should try in their best effort to rescue the player, not put them at risk. You can not keep a hostage for more than 5 minutes after this time is up you need to either let them go or kill them. You can not make a victims ransom more than 50k RP CASH or up to 10k gems. When taking a hostage you are only allowed to do it in a place that you can't be seen or is not visited by many people. You also can mug people anywhere if no one is in that area; sheltered and private., and properly roleplayed in order to avert power gaming. You can kidnap with a melee weapon under the rule that gun beats blade, and you can not kidnap in the mines.