By Sui-Lee Wee BEIJING (Reuters) - Early last month, 15 people went to a Beijing apartment to mark the 25th anniversary of the crushing of pro-democracy protests around Tiananmen Square. Among them were scholars, a prominent Chinese human rights lawyer, writers and the mother of a student who was killed by soldiers on June 4, 1989. A few days later, five were in police detention after a photograph of the gathering circulated on the Internet. It's the first time authorities have charged anyone for commemorating the Tiananmen crackdown privately in a home, activists said, showing China's determination to snuff out any mention of an event that riveted the world and convulsed the ruling Communist Party.