I am wondering if my mom is getting scammed? This is an Auto Trader car scam. Here's a rundown:

My mom put up an ad for her Toyota 4 Runner on AutoTrader. She got a response from a Nigerian pastor living in Toronto (where the ad was posted). He said he wanted a vehicle for his son. I was immediately skeptical but he wanted to come look at the car in person so I said that would be okay if I was present.

So when he comes to see the vehicle, he shows up 4 hours late with his "brother". Right when he arrives he hands me a brochure for his church and starts "blessing" our home. Anyways after we take it for a test drive we start trying to arrange the price. We told him we were firm on the price, he nowww mentions this is for a famous Nigerian priest who is coming to Canada and this is his gift. Not for his son anymore, this raised more alarms for me. Eventually he agrees to our price of $6000 cash. He tells us the money is coming from Nigeria and it will take a week. To hold it for him we settled on a $1000 cash deposit, again reminding him this sale must becash only. We go to the local bank with him and he pulls out $1000 and we draft up a small agreement stating he made a $1000 cash deposit and owes $5000 cash to complete the sale. We shook hands and left.

We didn't hear anything from him for 3 weeks. Eventually we got a hold of his cellphone but someone else answered saying he bought another vehicle. We told this person to get the original buyer to contact us. 2 weeks later he calls us saying he was in a terrible car accident (which I don't believe) and the money is coming. We told him it has been too long and he needs to come back for his deposit. He said he still wants the vehicle and will call us back that evening and arrange a day where he can pay and pick up the truck.

Its been 2 weeks since that phone call and we haven't heard anything. We haven't spent the money, but are wondering if there is anyway he can scam us. I feel like I got all the bases covered: local/in person sale, cash only, no wire transfer, signed agreement etc.
Should we just forget about it and keep the money? We have given him a fair amount of time.