WATCH: Police learn Sarah Stern put away over $25K shortly before disappearance: Part 5

WATCH: Police learn Sarah Stern put away over $25K shortly before disappearance: Part 5

Transcript for Police learn Sarah Stern put away over $25K shortly before disappearance: Part 5

Another day of searching for the New Jersey teen. The search for her remains is focused on the shark river inland. Her car, 1994 delta 88, was found on the bridge over the shark river. A reward is now being offered in this case, of course. Police are saying at this point if anyone has any information, on the whereabouts on 19-year-old Sarah stern, from Neptune, to please give police a call. She seemed very happy. She asked me to hang out that night. Carly draper had an encounter with Liam and Sarah the day Sarah went missing. And she was telling me that she wanted to move to Canada. She hugged me, and I was like love you. And she’s like love you too. And that was the last time I saw her. As if her disappearance wasn’t mysterious enough, it turns out there’s another big twist in this case, Sarah appears to have come into a large sum of cash. Sarah, her family had a second home in avon-by-the-sea. A couple months before she disappears, she’s with Liam, apparently, and, discovers a shoebox full of cash left by her, her late mother. She had spent about $10,000 of it, and put the rest in a safety deposit box at carney bank in Bradley beach. In the hours before she disappeared, Sarah went to the bank. One of her cousins got a message from one of the, the assistant manager at the bank who said just, you know, “By the way, Sarah was here yesterday afternoon.” That’s when the police get told, and then, we send the subpoenas and we get the surveillance footage, and then, the bank records. We of course wanted to know what time she accessed the box and what the contents of the box was, if there was anything that had remained in there. The bank has a two-key system. So the bank maintains a key, and the customer has a key, pull the box out, open the box up, and find $25,250.00 in 50s — 20s, 50s, and 100s. My first thought was wow, this is a lot of money. Then it was this is all old, old currency. It was in a very bad condition. After finding this money, Sarah immediately called her aunt Linda Stitely. Linda told her, “Don’t tell anyone about this.” Sarah unfortunately didn’t listen to that advice. Police learn that she has a safety deposit box with a lot of cash in it. Does that tell them where to go or who the suspect is? No, but it’s certainly something they’re going to want to follow up on. Before Liam had stopped talking, detectives had asked him about the bank. Liam had failed to tell us that he had gone to the bank with Sarah. Liam had only told us about the fact that they left the house one time. And Sarah and I went to taco bell. Which taco bell did you go to? The one in Neptune. Okay. Did you eat there? No. We went back to her house. Okay. Did you stay there T whole time after you went back to her house? Yeah. We actually went up into her room to play some video games. We were able to view surveillance video recordings captured from across the street, and what we saw was that Sarah and Liam had actually left the house in a car two times. So we of course were interested in knowing where did they go that second trip. Did you go to the bank? I was with her. Okay. What’d she do at the bank? Why did she stop at the bank? Just something to do with her money. I don’t know. She had found money in the Avon house a few months ago, and she has a lockbox full of money in there. I don’t know if she was taking money out, putting money in there. How much money? I couldn’t tell you. She never told me. She said it could be — she told me a range. She said it could be from $20,000 to $100,000. She wasn’t sure. Did she give you any of the money? No. Police find bank surveillance video of the day Sarah went missing and she’s inside the bank seemingly very happy, light hearted. She even waves goodbye to the bank manager and this is the last time we see her face. In my mind it eliminated the possibility that she ran away. You know, at 19 years old, if you have access to $25,000 in cash and you’re running away, I would think that you would want to take that with you. At that point, we had already located social security card, her passport as well as Canadian and U.S. Currency inside her bedroom. Finding that currency inside her safety deposit box told us that it was highly unlikely that she would have left. Police continue to search. There are numerous police departments working on this missing persons case, and they continuously come up with nothing. We didn’t have any answers. No sign of Sarah stern anywhere, no sign of a body. Uh-huh. My impression was is that this would end up, just end up turning into a cold missing person’s case because we had nothing. No indication she committed suicide. No indication that she did, in fact, leave the area willingly. No indication that she was murdered. It definitely never made sense to me, she loved everyone, so for her to leave without a trace and, you know, not say goodbye to her friends and family, that’s that’s not Sarah. That wasn’t Sarah. Her ability to disappear and move to Canada and create some fake identity was never really plausible. The suicide angle of it was a little more believable. One detective, Brian weisbrot, told me the first time I met him that he wouldn’t stop looking for Sarah. He wouldn’t stop until he found out what happened to her. And then police started to realize that maybe this wasn’t a suice and Sarah didn’t run away. Neptune police force. This girl that we thought had killed herself, all of a sudden there was a major break in the case. The entire theory of our investigation changed right then and there. I got a call one day, and it was the detectives, they said, “Just sit down, we want to tell you something.” The person who turns this whole case upside down, jumping right out of the Neptune high yearbook, fittingly voted most likely to become famous. A young film maker is about to become responsible for one of the most chilling videos you will ever see. When you saw the video — Uh-huh. — What was your reaction? First thing I thought was how Michael stern is going to feel about this when he finds out exactly how his daughter died. I’ve been describing it as pure evil. Pure evil. Parts of me I didn’t even know.

This transcript has been automatically generated and may not be 100% accurate.

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