My Employee Exhibited Symptoms Of Impairment (like He Was Drunk

my employee exhibited symptoms of impairment (like he was drunk or high on drugs), in fact, our customer thought he had cerebral palsy based on his speech and gait. His speech was slurred, his eyes were blank (not glazed over), and he complained of excessive tiredness. He was able to answer questions, but was delayed and deliberate. He tested negative for drugs and alcohol. Any thoughts? We are concerned.