his friends was selling a 1999 bmw. >> we go over there and look at it. you know, she loves the car. and i'm like, you know, let -- let's just sit back, you know, a day or two. think about it, you know. because they break down. it's expensive to fix. >> no. i don't see her sitting around, thinking about it. >> no, not at that age. she comes over, like, two days later she's like, "you're coming with me to get this car right now. i want that car." >> and so she got it. >> did she post her brand-new bmw -- >> oh my god -- >> all over social media? >> all over social media. >> was that how you could tell sarah was happy? by looking at her instagram, twitter, or facebook? >> yes. besides that, she was just so happy all the time. you know, to get her to be mad was very hard. >> and on the night of friday, june 6, 2014, nick says sarah was happy. she had recently broken up with a boy she'd been dating for two years and was looking forward to a night out with friends. nick had agreed to babysit jocelyn and nothing seemed out of the ordinary when