SAN FRANCISCO — Police announced, Friday, that they have arrested a suspect in this week’s fatal shooting of a man on a San Francisco subway commuter train. Javon Green, 26, was arrested, Thursday, in Pittsburg, a city about 40 miles east of San Francisco, after police released a still photo from surveillance video of a man they described as a person of interest and asked anyone with information to contact authorities, said Officer Kathryn Winters, a spokesperson with the San Francisco Police Department.