in bogdanovich, a desire for the eternal ingenue. >> where does one's career go from here?n too quickly. because if you rush things and you make the wrong decisions, it could be over very quickly. >> the real tragedy of dorothy's life is that she couldn't live long enough to really ever tell her own story. she never was able to say, "okay, this is what got me here but now these are the things that i want to be. here's who i actually am." >> the rays of the sun are slowly shining brighter. the evening will be forever yet time was not enough. ♪ >> her life cut short at just 20 years old. >> she never got the chance to define herself. that's "20/20" for tonight. i'm david muir. >> and i'm amy robach. for all of us at "20/20" and abc news, good night.

director peter bogdanovich. >> i'm in the middle of another movie called "they all laughed."ng. >> it was absolutely a movie about peter. very auto biographerical. >> will you marry me? >> okay, i will. >> you will? >> why, yes, after my divorce. >> there were fireworks, and i could tell that he was crazy about her. >> she moves essentially out of the hotel she's saying in for production and moves in with him. they ray try to keep it sea cor, but the world finds out. >> when you're comparing fillet mignon to hot dog on a stick, there's a big difference. >> reporter: but paul was not going to let her go easily. >> for paul, losing dorothy to peter bogdanovich was like the ultimate insult, because petter in his own way was a much paul. he had discovered a star. just like when he found her it at the dairy queen. >> i just knew he was capable of doing harm and she should be really careful. he's the kind of guy that could kill her. >> reporter: when she asked him for a divorce, paul became distraught and angry. >> it was after dorothy confessed that she loved bogdanovich and wante

>> okay, i will. >> compared to paul, bogdanovich was a prince.fference. >> reporter: between her newfound success and love affair with bogdanovich, dorothy decided to separate from snider. >> so she drove to his house and met with him there. >> she never felt there was any danger with anything with paul. >> and then bang. she was murdered. >> now, after killing stratten, snider turned the gun on himself. her life and death have inspired countless books and movies including bob fosse's classic film "star 80." >> i remember that. you can see the special on a special two-hour "20/20" airs at 9:00, 8:00 central right here on abc. cecilia? >>> we turn to our series on the secrets of tiktok, and what parents need to know. experts are raising concerns that young kids using this popular app could be exposed to inappropriate content. becky worley is here with a closer look. good morning, becky. >> reporter: tiktok has over a billion users according to industry estimates. it's that hot, and young children seem to flock to the app. u may think it's fun, lip