Section 7A. In any claim for compensation where the employee has been killed or found dead at his place of employment or, in the absence of death, is physically or mentally unable to testify, and such testimonial incapacity is causally related to the injury, it shall be prima facie evidence that the employee was performing his regular duties on the day of injury or death and that the claim comes within the provisions of this chapter, that sufficient notice of the injury has been given and that the injury or death was not occasioned by the willful intention of the employee to injure or kill himself or another.