DARTMOUTH, Mass. — An investigation is underway after Dartmouth police fatally shot an armed domestic violence suspect who opened fire at officers.The Bristol district attorney's office says officers responded to an apartment in town at about 11 p.m. Thursday after receiving reports that a man had entered his ex-girlfriend's apartment and damaged her television and computer.The man had left the scene by the time police arrived, but called to say he was coming back armed and didn't want to go back to jail.