Former President Bill Clinton has told the BBC the US political climate must change after the shooting of a US Congresswoman and others in Arizona.
"No-one intends to do anything that encourages this sort of behaviour," he said. But political rhetoric "falls on the unhinged and the hinged alike".
Some commentators suggest the vitriolic political rhetoric in the US may have contributed in some way to the attack.
A Mass for victims of the shooting was held in Tucson on Tuesday night.
Hundreds of mourners attended the service, described as a "Mass of healing for our community", at a church a few blocks from the scene of Saturday's attack.
"We are a community questioning, wondering and struggling with how such violence could happen. We wonder how God could allow such violence to happen to innocent people," Bishop Gerald Kicanas said.
Jared Loughner, 22, has been charged over the shooting, in which six people were killed, including a federal judge and a nine-year-old girl, and more than a dozen injured. In an initial court appearance on Monday he was ordered jailed pending trial.
"We don't understand why this happened. It may not make any difference, but we wish that we could change the heinous events of Saturday," Mr Loughner's parents said in a statement.
"We care very deeply about the victims and their families," they added. "We are so very sorry for their loss."
Speaking on a trip to Haiti, Mr Clinton called on the US House of Representatives to "lead the way" in toning down the political discourse.
"We cannot be unaware of the fact that - particularly with the internet - there's this huge echo chamber out there," he said.
"This is an occasion for us to reaffirm that our political differences shouldn't degenerate into demonisation, in the sense that if you don't agree with me you're not a good American.
"I'm hoping there will be a lot of good debates that go beyond turning this into politics... about how and why it happened and what else we can do to minimise those things."
Meanwhile, Arizona Governor Jan Brewer signed emergency legislation into law on Tuesday evening, prohibiting protests within 300ft (91m) of a funeral or burial service.
The Westboro Baptist Church, which has held protests at military funerals in the past to draw attention to its stance on homosexuality, has said it plans to picket the funeral on Thursday of the nine-year-old girl killed in the shooting.
Earlier on Tuesday, doctors said US Congresswoman Gabrielle Giffords, the Arizona Democrat who was the intended target of the shooting, was still in critical condition in hospital but was capable of breathing on her own.
"She's holding her own," said Michael Lemole, a neurosurgeon who operated on Ms Giffords.
The White House has announced that President Barack Obama will attend a memorial service on Wednesday evening at a basketball arena in Arizona.
He will address the crowd, and the service will include a Native American blessing, a moment of silence and a poetry reading.
Meanwhile, as the debate over personal security for US Congressmen - who typically have little or none - heated up in Washington DC, the US Senate sergeant-at-arms told US television he opposed lawmakers arming themselves against potential threats.
"I don't think introducing more guns into the situation is going to be helpful," Terrance Gainer said.
But he acknowledged that there had been 49 threats against US Senators over the past year, an increase on previous years.
Mr Loughner has been charged with five federal crimes - the attempted assassination of a member of Congress, the first degree murder of two federal employees and the attempted murder of two federal employees - and may face additional state charges.
Magistrate Judge Lawrence Anderson scheduled a preliminary court appearance for 24 January.
Mr Loughner is represented by Judy Clarke, a prominent defence attorney who represented an infamous parcel bomber and the man convicted of setting a bomb at the 1996 Olympic games in Atlanta. He did not contest the detention order.
The attack occurred on Saturday during an open-invitation meeting at a Safeway grocery store in Tucson, Arizona, which Ms Giffords had arranged for constituents.
Ms Giffords, 40, was shot from close range by the gunman, who then began shooting into the crowd. Among the dead were a nine-year-old girl and a federal judge.
It is unclear whether the US justice department will seek the death penalty against Mr Loughner, should he be convicted.
A total of 19 people were shot.
Flags across the US were flown at half mast on Monday, and Mr Obama said the nation was "grieving and shocked".