The 20-year-old man opened the bag that he thought contained four iPhones that had been advertised on Craigslist.
He found empty boxes.
He told police that he yelled at the man walking away with his $1,600 in cash. That 29-year-old reached into his waistband, indicated he had a gun and told him to back off.
"Our victim was pretty shaken up by the turn of events," Lt. Doug Nolte of the Wichita police said Thursday.
The incident pointed out the need to be cautious when buying articles from strangers online, police said.
The reported robbery took place at 9:30 a.m. Wednesday in the parking lot of the Walmart at 29th Street and Rock Road.
"This is a situation where someone was intentionally set up," Nolte said.
Online advertising can also leave a trail of information. The 29-year-old had been arrested by 4 p.m. Wednesday, according to jail booking reports.
"This was good, old-fashioned police work," Nolte said. "Officers went above and beyond and tracked down every piece of information they could."
According to police reports, this is what happened:
A man in Manhattan had seen four iPhones advertised on Craigslist at $400 apiece. After learning the people selling the phones were in Wichita, he called a friend here and arranged for the 20-year-old to make the purchase.
The Manhattan customer sent a check for $1,600. His friend cashed it and took the money to the parking lot.
After handing the older man the cash, the 20-year-old told police he thought the package felt light. He opened up one of the boxes and found only the owner's manual and charger — no phone.
When he asked the man about it, he said he had a gun.
The 20-year-old man got into his car and waited for the other man to leave.
Police think at least one other person is involved and may make more arrests.
"We haven't recovered all the money yet," Nolte said.