LAS VEGAS, Nevada (CNN) -- With O.J. Simpson looking on from the defense table, a sports memorabilia dealer testified Thursday that the former football star helped lead a September "military-style invasion" of a Las Vegas hotel room.
Dealer Bruce Fromong said he never saw Simpson carrying a gun during the incident, but at least two of the men accompanying Simpson were armed.
Simpson ordered his associates to keep Fromong and another dealer, Alfred Beardsley, in the room as sports memorabilia was removed, Fromong testified.
He quoted Simpson as saying, "Don't let anyone out of the room. Nobody leaves."
Fromong said Simpson also insisted that the merchandise the dealer had been trying to sell at the Palace Station casino was "all my s***."
Also Thursday, prosecutors played six-minutes of the audiotaped confrontation, in which Fromong tried to reason with a clearly angry Simpson.
After Simpson and his associates left, Fromong could be heard saying, "We were just robbed at gunpoint by O.J .Simpson."
Thomas Riccio also testified Thursday. He set up the meeting between Simpson and the memorabilia dealers and is the one who made the audio recording of the incident. Simpson decided to go ahead with a sting operation to retrieve stolen merchandise, Riccio said on the stand.
One man in the group with Simpson pulled a gun during the incident, he said.
Riccio testified that after Beardsley approached him with an offer to sell stolen Simpson merchandise, he contacted both Simpson and the police. But the police refused to get involved in what they believed was a civil matter.
Riccio said he also talked to the FBI about a plan to get Beardsley to admit on video that the material was stolen, then sell the video as an exclusive.
Simpson said he wanted to keep the items for his family, not sell them, Riccio testified.
Riccio also said that at a party before the incident at the Palace Station, Simpson talked excitedly about the plan to get the merchandise back -- and was urged by his family not to do it.
Thursday's testimony by Fromong and Riccio that guns were used contradicted Simpson's assertions in media interviews that no guns were involved in the confrontation with the dealers. Simpson has insisted the incident was merely an effort to retrieve memorabilia that belonged to him.
But prosecutors allege Simpson, 60, was the ringleader of the alleged Palace Station robbery, and he faces 12 criminal counts -- including conspiracy, kidnapping, robbery, burglary, coercion and assault with a deadly weapon -- that could land him a life sentence if he's convicted.
He has pleaded not guilty.
The preliminary hearing is to determine whether there is enough evidence against Simpson and two co-defendants -- Charles Stewart and Charles Ehrlich -- to warrant a trial.
Prosecutors were expected to call eight witnesses, including three of Simpson's former co-defendants who have reached plea deals on lesser charges and are expected to testify that guns were involved.
Simpson, who is free on $125,000 bond, came to court nattily attired in a light-gray suit, silk pocket square, white shirt and striped tie. Journalists filled more than half of the 100-plus seats inside the courtroom, while news helicopters circled outside.
Fromong testified that the chain of events that led to the September 13 confrontation began in the Palace Station's parking lot, where he and Beardsley met with Riccio, who was supposedly representing a buyer interested in Simpson merchandise. Watch Fromong talk about his former business relationship with Simpson »
Riccio asked them to carry the items into the hotel room so the buyer could inspect them, Fromong said.
Once the men were inside the room, the door burst open and a group of men, including Simpson, entered, Fromong testified.
During the encounter, which lasted five to six minutes, Fromong said, one of the men drew a semiautomatic weapon and pointed it at him, while another man had a gun in his belt. Simpson must have seen at least one of those weapons, he said.
Riccio, who said he was given immunity for his cooperation in the case, later sold the audio recording of the encounter to the gossip Web site TMZ.
Among the 600 to 700 items Fromong said he had for sale were presentation balls, plaques and ties worn by Simpson during his criminal trial for the 1994 murders of his ex-wife, Nicole Brown Simpson, and her friend, Ron Goldman.
Simpson was acquitted after one of the most sensational trials in American history, but a civil jury later found him liable for their deaths, slapping him with a $33 million judgment.
Fromong testified he also had items at the Palace Station that he bought from Mike Gilbert, a former business partner of both Fromong and Simpson who is also in the sports memorabilia business.
He acknowledged telling Simpson during the encounter that "Mike took your stuff," referring to Gilbert.
Fromong insisted he owned all of the memorabilia he was trying to sell, including items he bought from Gilbert. He said he had canceled checks written to Gilbert for the items he bought.
Fromong denied he is trying to profit from the September incident. While acknowledging some contacts with television networks, he said he has not entered into serious discussions with anyone "in the business" about a possible book or movie deal and has no book contract.
However, Simpson attorney Gabriel Grasso did get Fromong to concede that "at one time" while in the room, Simpson told his cohorts to take only what belonged to him and leave the rest of the merchandise. The dealer also mistakenly said everyone who entered the room was black, when two of the men were actually white.
Fromong, who suffered a heart attack shortly after the incident, acknowledged on the stand that he takes prescribed medication, leading Grasso to suggest that could be the reason for his misidentification.
Under questioning from Ehrlich's attorney, John Moran, Fromong said he did not remember telling a 9-1-1 operator after the alleged robbery that he was going to his truck to get his gun, although he conceded that a transcript of the call shows he made that statement.
Fromong said he did have a gun in his glove compartment that day, which he said was his normal practice. E-mail to a friend
CNN's Peter Ornstein contributed to this report.