Dr. Aaron Glassman is the president and a doctor at St. Bonaventure Hospital. He's somewhat of a fatherly figure to Shaun and he's highly supportive of him, and he gets concerned when something is bothering Shaun.
Aaron has been a doctor for at least 20 years (the exact length of time is unknown).
Around a decade prior to the start of the show, he met Shaun and Steve Murphy when they arrived at his office on foot. The brothers had hoped he would be able to save Shaun's pet rabbit, though it had already died when their father threw it against the wall. When Steve asked if the rabbit had gone to heaven, Glassman awkwardly replied he was sure that was what had happened.
By the time Shaun and Aaron reconnected, Steve had died and Shaun was to be taken back to his parents. He refused to go home, and police were lost on what to do with him. Glassman decided to take the boy in for the night, "and tomorrow we'll figure out the rest." Ultimately, he ended up acting as a surrogate father to Shaun well into the future.