A 23-year-old suspect identified as Michael Martinez is accused of robbing a man who answered an online ad to buy his iPad. But San Antonio police said Martinez later tried to pose as the victim in the case.

An arrest warrant affidavit stated that an 18-year-old man reported the crime in November, telling San Antonio police that he had answered an ad that Martinez placed on Craigslist.

The man said he later met up with the suspect, and made a deal to trade his laptop computer plus $100 for Martinez's iPad, the affidavit stated.

While finalizing the deal, the man said, Martinez pulled out a knife and robbed him, the affidavit stated. It appeared both men suffered cuts in a struggle over the knife.

Police said after the other man reported the crime, Martinez claimed that he was the one who actually had been robbed.

The affidavit stated that investigators made several attempts to meet with Martinez, but he failed to show up at those meetings.

When they finally talked to Martinez, detectives said he was defensive, the affidavit stated. Martinez was arrested Tuesday on a charge of aggravated robbery.

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