Michael McDermott, a 43-year-old computer software engineer, claims he is insane.

McDermott said the archangel St. Michael appeared to him 12 days before the Dec. 26, 2000, shootings and told him he could travel back in time 60 years and prevent millions of deaths if he killed Hitler and the top "architects" of the Holocaust.

In great detail, he then described being in Hitler's bunker, hearing Hitler's thoughts and shooting the Nazis.

"The whole idea was to prevent Nazi supremacy," McDermott said.

Prosecutor Tom O'Reilly, however, said McDermott is a skilled storyteller because of two decades of experience with Dungeons and Dragons, a fantasy role-playing game.

"And that's something you've been involved with for 20 years -- concocting stories?" O'Reilly said.

"It's not so much concocting as having fun, participating in a group fantasy ...," McDermott replied.

Days after the prosecution described how McDermott walked through Edgewater Technology's Wakefield offices firing his AK-47 and shotgun, McDermott did the same, but claimed he saw Nazis, not colleagues.

"There were two men and a woman in front of me. Both of the men had swastika armbands. I immediately shot both of the men," McDermott said.

Under questioning from his attorney, McDermott said he shot three more "Nazis," then he heard "Hitler's thoughts" coming from the accounting office, where victims Paul Marceau and Rose Manfredi were killed.

"The last Nazi was there. I shot and killed him. And Hitler was there. I shot and killed him. My mission was complete. I knew at this point I had a soul."

After the shootings, McDermott returned to the reception area where he was arrested. He told the jury he died at a police station in Berlin from the painkillers and vodka he downed before the shootings.

McDermott was often glib in his testimony and sometimes looked at the jury as he launched into long, detailed explanations.

At one point, when he was explaining why he believed he was born without a soul, he addressed the jury directly, saying most people -- including the jurors -- have a moral compass and know instinctively the difference between right and wrong. He said he has to give it careful thought.

Prosecutors say McDermott planned the slayings in retaliation for the company's plans to withhold his wages to pay $5,600 in back taxes owed to the IRS.

McDermott acknowledged on the stand that he bought a book, "Clinical Assessment of Malingering and Deception," which helps detect when someone is faking mental illness, and downloaded Internet material about faking psychological disorders.

Midway through McDermott's explanation of the shootings, a male relative of a victim got up, uttered an obscenity, and left the courtroom. He was followed by nearly a dozen more relatives, some tearful.

Marcelle Marceau, Paul Marceau's mother, said the families of the victims were "very angry" about McDermott's story.

"This whole thing was rehearsed for a year," she said.

During cross-examination, McDermott was sometimes combative. At one point, when he apparently felt O'Reilly had mischaracterized his earlier testimony, he sarcastically replied, "Nooooooooo."

McDermott told the jury St. Michael gave him his mission moments after Edgewater informed him that his wages would be withheld.

"I felt great. For the first time in my life I felt I could achieve what everyone takes for granted -- that I could have a soul and go to heaven," he said.

When police arrived Edgewater's office moments after the slayings, they found McDermott with the weapons at his feet.

"I don't speak German," was all he said as he was being arrested, police said.

McDermott testified that he hears voices telling him what to do. He also said he's tried to commit suicide at least three times and was raped several times as a boy.

"The voices in my head, I clustered them into different groups," he said. "The major one I call the chorus. The chorus continuously tells me what a bad person I am, what a waste of space and skin and air I am."

One of the "non-chorus" groups, he said, tells him to steal things.

Defense lawyer Kevin Reddington walked McDermott through his history of mental problems, particularly relating to his past jobs. He tried to show a pattern of hallucinations, which culminated in the office shootings.

McDermott claimed, for example, that he was harassed by an ex-girlfriend who worked with him at a Maine nuclear plant. He claimed she called him repeatedly, but Reddington said an investigation showed that McDermott actually made the phone calls, which McDermott denied.

McDermott also claimed he was exposed to radiation, which "pretty much killed my thyroid."

Reddington, however, said a blood test showed "no evidence of radiation exposure, period, in the case."

McDermott said he got a vasectomy after his 1992 marriage. "I wouldn't want to pass my craziness to someone else and I had years of exposure to radiation," he said.