CENTENNIAL, Colorado (REUTERS) - After all 165 guilty verdicts were read and Colorado's movie massacre gunman was taken back to a cell to await his fate, many of his victims rejoiced and said James Holmes must be executed for justice to be done.

Survivors and their loved ones smiled and hugged outside the rain-swept courthouse on Thursday evening, after Holmes was convicted of killing 12 people and wounding 70 inside a Denver-area theatre.

The third anniversary of the rampage will be this Monday.

"As soon as we heard the first 'guilty' we knew the other dominoes were going to fall," said Tom Sullivan, 60.

His son Alex, called Sully by his friends and co-workers, had been celebrating his 27th birthday with friends at the cinema when Holmes killed him and the others in a hail of bullets.

"We're part of the way through this and ready for the next step," Sullivan, 60, told Reuters.

That next step starts on Wednesday when the trial enters the sentencing phase.

Jurors will hear more weeks of testimony, then decide whether Holmes should be put to death by lethal injection or serve a life sentence with no possibility of parole.

"I hope to do everything I can to see this guy's privileges are taken away and he no longer gets to breathe the sweet air that Coloradans get to breathe," Sullivan said.

Asked if he wants to see Holmes executed, Sullivan replied: "Yes. Absolutely."

PENALTY PHASE

Also outside the Arapahoe County Justice Centre was Marlene Knobbe, 79, grandmother of slain college student Micayla Medek, 23.

Knobbe said she was "thrilled" with the verdict.

"But I'll wake up tomorrow, and he's still alive, and that's not right," she said.

"I want him to die."

For Sullivan, Knobbe and others forever affected by the massacre, Thursday's unexpectedly quick verdict ended years of worrying whether a jury might buy Holmes' insanity plea.

But after hearing from hundreds of witnesses and seeing thousands of pieces of evidence during the almost three-month long capital trial, the nine women and three men on the panel returned guilty verdicts after just about a day and a half of deliberation.

Holmes, 27, remained expressionless, hands thrust into pockets throughout the hour it took for Judge Carlos Samour to read "guilty" after all 165 charges.

In the packed public gallery behind the defendant, some victims celebrated quietly, embracing and clapping each other on the shoulder.

During the penalty phase, jurors will consider aggravating factors, such as the murder of a child, the youngest victim, six-year-old Veronica Moser-Sullivan.

They will also hear mitigating factors presented by Holmes'court-appointed attorneys, who could even call the gunman's parents, Arlene and Bob.

DECISION LATE AUGUST

The process is expected to last until late August, when the jury will decide if Holmes should be executed for one of the worst mass shootings in recent US history.

Prosecutors rarely call for the death penalty in Colorado.

Currently, there are three inmates on death row, and only one death-row inmate has been executed in the state in nearly 50 years.

Jansen Young, a survivor who was wounded in the shooting and whose boyfriend was killed, said she would accept it if the jury gave Holmes life in prison.

But she said she was pushing for the death penalty because it was what her boyfriend Jonathan Blunk, 26, would have wanted.

Also outside court, Sandy Phillips watched some of the survivors leaving, including one being pushed in a wheelchair.

Her 24-year-old daughter, Jessica Ghawi, was in the theatre that night and died after being hit by several of Holmes' bullets.

"We're very happy that this animal, this monster, will never see the light of day," Phillips said.