A 25-year-old Brooklyn man was arrested for brutally stabbing his transgender East Harlem girlfriend to death, police said Wednesday. Equan Southall was charged with murder in the Aug. 1 death of Camila Guzman. They had been in a relationship for four months, police said. The suspect had five prior arrests, including grand larceny and possession of a concealed weapon, officials said. Police found Guzman lying face down inside her apartment at 170 E. 110th St. with multiple stab wounds to her back. She was pronounced dead at the scene.