Guillermo Söhnlein, the co-founder of OceanGate, the company that built and operated the Titan submersible, testified before a Coast Guard panel Monday that the cause of the implosion may never be known. » Subscribe to NBC News: nbcnews.to/SubscribeToNBC » Watch more NBC video: bit.ly/MoreNBCNews NBC News Digital is a collection of innovative and powerful news brands that deliver compelling, diverse and engaging news stories. NBC News Digital features NBCNews.com, MSNBC.com, TODAY.com, Nightly News, Meet the Press, Dateline, and the existing apps and digital extensions of these respective properties. We deliver the best in breaking news, live video coverage, original journalism and segments from your favorite NBC News Shows. Connect with NBC News Online! NBC News App: apps.nbcnews.com/mobile Breaking News Alerts: link.nbcnews.com/join/5cj/breaking-news-signup?cid=sm_npd_nn_yt_bn-clip_190621 Visit NBCNews.Com: nbcnews.to/ReadNBC Find NBC News on ...