An ex-Army officer, reportedly dismissed from service a few years ago on charges of insanity, died on Friday after being assaulted by some people in the Mahestala area in South 24 Parganas district. Jayanta Sarkar was said to have often resorted to violence. He was beaten up following an altercation and declared dead after being taken to a local hospital, officer-in-charge of the Mahestala thana Debashish Banerjee said.