A Tennessee National Guard recruiter charged in an armory shooting brought a loaded pistol into the building intending to kill himself, not shoot his fellow Guard members, his lawyer said Tuesday.

Defense attorney Michael Stengel delivered an opening statement in the federal trial of Amos Patton, who has pleaded not guilty to charges that he tried to kill four of his superiors at the National Guard armory in Millington on Oct. 24, 2013. Patton is accused of assaulting a major, a lieutenant colonel and two sergeant majors with a firearm, with intent "to do bodily harm" and commit murder. If convicted, he faces no less than 20 years in prison on the murder-related charges.

Prosecutors say Patton pulled a gun from a fanny pack and began shooting after a disciplinary meeting in which he was told about an official recommendation to remove him from his job as a recruiter and reduce his rank from sergeant first class to staff sergeant. The meeting came after an investigation into alleged misconduct by Patton.

In his opening statement, Assistant U.S. Attorney Fred Godwin told jurors Patton was called to the meeting at the armory and drove there in his government-issued car.

"When that meeting was over, Mr. Patton was unhappy," Godwin said. "Indeed, he was angry."

After the meeting, Patton and two superiors went to the car parked outside the armory, Godwin said. They were going to drive back to Patton's office in the Memphis suburb of Bartlett to take him to his personal vehicle.

Patton retrieved a bag and a fanny pack from the car, then asked to go to the bathroom, Godwin said. Patton entered the armory but was told by a superior that he could not go into the bathroom with both items.

Patton then reached toward the fanny pack, which was slung over his shoulder, and pulled out a 9mm pistol, Godwin said. One of Patton's superiors then tried to restrain Patton from behind with a bear hug, Godwin said.

Patton then fired six shots, wounding three soldiers, Godwin said. Patton ran out of the armory, was subdued by other Guard members and was arrested by Millington police.

Godwin said Patton took the loaded pistol and 50 extra rounds of ammunition to the armory with the goal of shooting someone if he lost his job.

Stengel, Patton's lawyer, disputed the prosecutors' claim, saying Patton wanted to go to the bathroom with the gun to commit suicide. Patton only fired the shots because he was being grabbed from behind, Stengel said.

"The shooting starts, wild shots, during this struggle, while he was in a bear hug," Stengel told the jury.

Before the disciplinary meeting, Patton told a confidant, identified as Sgt. 1st Class Kenneth Turner, that he intended to take out a gun and start shooting if he was fired, prosecutors said. Turner didn't forward the threats to his bosses, Godwin said.