Were Bruce's injuries on the set of Tears of the Sun the beginning of his physical and/or mental decline?

Of course, assuming if it's really true that he now has dementia:

https://www.theguardian.com/film/2004/nov/24/news1

Bruce Willis is suing the makers of his 2003 action movie Tears of the Sun for injuries allegedly sustained on the set of the film.

Willis's lawsuit against Revolution Studios claims that he suffered "extreme mental, physical and emotional pain" after an on-set incident in October 2002 when he was struck on the forehead by a "projectile" during the detonation of pyrotechnics by the film's special effects unit.

The lawsuit did not further specify the nature of Willis' injuries, but accuses Revolution and its special effects foreman Joe Pancake of incompetence in maintaining his safety. The financial damages sought by the actor are not specified, but the suit does claim that Willis "was required to and did employ physicians and other medical personnel," and that he will incur more medical expenses in the future relating to the incident.