More than just the son of a star, Andrew had a diverse performance portfolio spanning decades, from Kirk Cameron's friend "Boner" on the television sitcom Growing Pains, to an appearance on Star Trek: Deep Space Nine, to playing the villainous Joker in the acclaimed short Batman: Dead End — described as "one of the ten most pivotal moments in fan film history." More recently, he appeared with his father in the independent film InAlienable, written by the senior Koenig, the pair's only collaboration.
Andrew also used his celebrity status for humanitarian causes. As described on Walter Koenig's site:
Andrew was an activist his entire life and was best known to those who knew and loved him as a compassionate, ethical man who lived according to his conscience. He was a vegan, active in environmental causes, and in animal and human rights and was quick to take an active role to help on a grass roots level. Most recently, he had been working on behalf of the people of Burma, and was arrested during the 2008 Rose Bowl parade for protesting American involvement in China's Olympics due to China's support of the Burma military regime.
I was first notified that Andrew was missing by an email to Star Trek: Of Gods and Men fans. I hoped for a happy resolution, but Andrew had been suffering from clinical depression, in which good decisions are hard to make. If Andrew could've understood how many friends and family cared for him and how hurt they are, he may not have chosen this permanent solution to a temporary problem.