Can an employer be sued if an employee is injured by someone how is on high on drugs at time of injury?

A fellow employee was recently injured at work. He was working along side another employee moving a large set of metal stairs when for some reason it came down on employee's foot hard almost cutting it in half. He was placed on workmans comp., after that lite duty, now waiting to be released. Employee that caused the accident was terminated shortly after the accident happen to which only means that he was on drugs at time of accident. Because of his injury he will probably have some after effects as a result of this injury. I also need to know If he should be compensated for the pain he suffered with his injury.