TAMPA — Two years ago, a former Marine accused of battering his girlfriend fired nearly a dozen bullets at the Hillsborough deputy sent to investigate.Deputy Lyonelle De Veaux lived, and though authorities arrested Matthew Buendia and charged him with attempted murder of a law enforcement officer, his girlfriend stood by his side. Jessica Gipson visited the defense attorney's office several times a week, providing information in Buendia's favor.In October 2011, that ended. Jessica Gipson broke up with Buendia and the defense lost the cooperation of one of its best witnesses. The reason? A U.S. Department of Homeland Security agent approached her with information that Buendia had an affair, defense attorney Mark O'Brien says she told him. She wouldn't say who that agent was.Buendia, 26, says the alleged affair is a lie, according to O'Brien. They want to know more about this so-called agent. As far as they know, federal agents have not been investigating Buendia.Was it someone trying to drive a wedge between witness and defense, the attorney wonders. Could it constitute witness tampering?On Wednesday, O'Brien asked a judge to order Gipson to name the agent. And Circuit Judge Ronald Ficarrotta did.He denied Gipson's claim that the information was privileged — that she didn't have to share a name because she risked self-incrimination.O'Brien hopes to schedule a deposition and have an answer in the upcoming week. He believes an answer will help in his preparation for the trial, scheduled to begin Dec. 2.According to authorities, on Sept. 30, 2011, Buendia approached Deputy De Veaux outside his Carrollwood apartment complex as the deputy talked to Gipson about her domestic violence call.Buendia pulled out a handgun and fired nine or 10 times at De Veaux, deputies say, from just a few feet away. Three bullets hit her — in the upper leg, lower leg and shoulder.As she lay on the pavement, Buendia ran back into his apartment and locked himself inside. Within minutes, dozens of SWAT members and negotiators descended. A negotiator on a bullhorn told Buendia to surrender. Deputies threw chemical canisters into the apartment to force him outside.They blew up the apartment door and sent in a robot with a camera. It combed the apartment and sent an image of Buendia passed out in a closet. They arrested him and he has spent the last two years in solitary confinement, wearing a red uniform that denotes "high-risk" inmates.His family and attorney have said Buendia suffers from PTSD after three military tours abroad, including one in Afghanistan and one in Iraq.On Wednesday, O'Brien said his client has also suffered from dissociative disorder and was having an episode when he shot at the deputy. Dissociative disorder was formerly known as "multiple personality disorder," and during dissociative fugue a person might not be aware of what he is doing — or might not remember the actions later.O'Brien believes Gipson has good intentions and is perhaps being manipulated by someone else."I can understand why she's upset with Mr. Buendia," he said. But the information she was given was not done so in any official capacity, O'Brien claims. So why was it shared with her at all, he asked.Two agencies with access to Buendia's letters or phone calls are the Hillsborough County State Attorney's Office and the Hillsborough County Sheriff's Office, which runs the county's jails.O'Brien did not want to speculate if either agency was involved — or what their motives may be."I don't need to," he said. "I should know within the next week."Sheriff's Office spokesman Larry McKinnon said Wednesday the agency is aware of the legal proceedings and is "looking into the matter."Jessica Vander Velde can be reached at [email protected] or (813) 226-3433.