Sounds like someone was anticipating something could go wrong and was prepared for it. Was it the homeowner that ended the situation?
If there were three in custody I would say someone called the cops. Before or after the transaction is the question.
Here's the brilliance of the criminals: The man who was robbed was the seller, but it was not at his house. He went to the buyer's apartment to complete the sale. The buyer answered the door and pulled the seller inside at gunpoint. They then pistol whipped and robbed the seller before kicking him out of the apartment. So what did the victim do, of course he went to the police. The police went back to the apartment, arrested 6 people and recovered two stolen firearms. Dumbest criminal of the day award goes to.....!!! https://okcfox.com/news/local/okc-man-robbed-at-gunpoint-after-attempted-sale
Oh LORD!! You guys making fun don't remember when a BUNCH of us went to an early morning deal for one of the members here who thought his seller seemed hinky?? It was a stinking RIOT! Scared the guy plumb to death. AND THEN Grumpy pulled up in his patrol car (he was working nights then and the meet time was when his shift ended). I thought emo kid was gonna BOLT! Lmao! Then we all went to breakfast at IHOP in Bricktown. Man ... Those were the days! Lol