They heard grisly details about the shooting of seven Internet company workers, but the jury who will decide the fate of accused killer Michael McDermott heard nothing about his claims of insanity during opening statements Thursday.

Prosecutor Thomas O'Reilly instead told jurors how McDermott methodically walked through Edgewater Technologies on December, 26, 2000, and shot seven co-workers dead while passing others at random.

"There will be no doubt in this trial ladies and gentlemen that Michael McDermott is guilty beyond a reasonable doubt," O'Reilly told the jury.

A memorial for the victims near where they were shot while they worked at a Massachusetts Internet company.

Defense lawyer Kevin Reddington declined Thursday to present the expected defense argument that McDermott committed the killings, but suffered from a long history of mental illness, financial troubles and was insane when he went on the rampage in a Wakefield, Mass. office. Reddington reserved the right to give his statement at the conclusion of the state's case.

If convicted of seven counts of murder, McDermott faces life in prison. Massachusetts has no death penalty. He would be committed to a mental institution if the jury agrees he was insane.

The burly, bushy-haired defendant sat reading a book as the prosecutor described the gruesome scene on December 26, 2000.

McDermott, after celebrating Christmas with his family the day before, arrived at work like any other day — but was led out in handcuffs before noon, leaving behind seven dead bodies.

Several employees called 911 to report witnessing the software tester walk through the vast office armed with a shotgun, an assault rifle, a semi-automatic handgun and a bag full of ammunition.

The shooting came two weeks after company vice president Cheryl Troy told McDermott that payroll would be garnishing his paycheck on behalf of the Internal Revenue service. McDermott owed $5,600 in taxes.

"Michael was upset. He had tears in his eyes. He became angry," O'Reilly said, adding that McDermott told Troy, "You do not have to do this."

Troy, however, told McDermott that the company had no choice. Troy was among the seven victims.

In the days leading up to the shooting, the prosecutor explained, McDermott's car was spotted in his Haverhill neighborhood by witnesses who reported hearing gunshots. When police arrived, they found several shells. Earlier that day, on December 24, 2000, a representative from Chrysler contacted McDermott to inform him that his 1994 Plymouth Acclaim would be repossessed, O'Reilly said.

McDermott parked his car blocks away after that, the prosecutor said — but two days later, on the day of the shooting, McDermott received another phone call at work from Chrysler. This time, however, he told them to pick up the car — that he would not be needing it anymore, O'Reilly told the jury.

Three minutes later, he got up from his desk with his cache of weapons and walked to the reception area, where he gunned down office manager Janice Hagerty and then shot Cheryl Troy.

He proceeded toward the human resources department, passing some employees without incident before opening fire on Jennifer Bragg Capobianco, Craig Wood and Louis Javelle.

McDermott then walked to far end of the building to the accounting office — the department that would be responsible for the payroll deductions for the IRS — and used a shotgun to shoot off the locked door knob. Once inside the office, the prosecutor said, he shot and killed Rose Manfredi and Paul Marceau.

O'Reilly told the jury that several employees will give eyewitness accounts.

One witness, the prosecutor said, will testify that she watched as McDermott lifted a weapon with his left hand, fired multiple shots and that, seconds later, she heard "escaping air and gurgling coming from Rose Manfredi."

Following the trial's opening inside Judge R. Malcolm Graham's Cambridge, Mass., courtroom, jurors were taken on a tour to the Harvard Mills office complex where Edgewater Technologies is located and to McDermott's neighborhood in Haverhill.