A man is dead after the Medford commercial building where he works caught fire, according to authorities.Medford police said the Massachusetts city's emergency communications center was first notified about the fire at approximately 4:20 a.m. Sunday.Police officers and firefighters discovered a commercial building at 58 Swan St. was burning when they arrived at the scene and struck a second alarm shortly thereafter.According to Medford police, a person arrived at the scene and informed officers that he knew an employee had been sleeping inside the business. Firefighters found the man inside a bathroom and began providing medical aid.The employee, who has not been identified, was transported to Massachusetts General Hospital in Boston, where he later died of his injuries.Medford police did not specify which the commercial building where the fatal fire happened. A WCVB photographer captured video of crews boarding up the Eastern Tool Corporation building on Sunday.The state's Office of the Chief Medical Center is working to determine the cause of the man's death.The cause of the fire is unknown at this time and is being investigated by the Medford Police Department, Medford Fire Department, Massachusetts State Police, Middlesex District Attorney's Office and Massachusetts Department of Fire Services, which is also known as the State Fire Marshal's Office.