A Harwich man was charged with trying to rob a convenience store armed with a grenade that turned out to be fake.

Police said a masked Dennis Walsh walked into the store on Sunday night holding the grenade and demanded money from the cash register while threatening to pull the pin.

Walsh fumbled with the pin, according to police, then got scared by a store employee and tried to escape. Three witnesses chased and grabbed him.

Walsh is charged with armed robbery while masked, assault to rob while armed and assault with a dangerous weapon.

He is scheduled to be arraigned Monday in Orleans District Court.