Planned Parenthood said on Sunday that news reports that the gunman who attacked its Colorado health clinic had uttered "no more baby parts" during his arrest showed that the suspect was motivated by an anti-abortion agenda.

The remark attributed to the 57-year-old suspect, identified by police as Robert Lewis Dear, was an apparent reference to Planned Parenthood's abortion activities and its role in delivering fetal tissue to medical researchers, a hot button issue in the 2016 race for the presidency.

"We now know the man responsible for the tragic shooting at PP's health center in Colorado was motivated by opposition to safe and legal abortion," the organization said on Twitter.

Conservatives have accused Planned Parenthood, a nonprofit that provides a range of health services, including abortion, of illegally selling baby parts, an accusation it has strenuously denied.

Dear, a 57-year-old South Carolina native who moved to Colorado made the remarks during his arrest after standoff lasting several hours at the Colorado Springs clinic on Friday, NBC News and other media outlets reported.

Reuters was unable to independently confirm those reports of Dear's comments though the reports cited unnamed law enforcement sources.

While Dear's remarks could hint at a possible motive for Friday's rampage, NBC's sources stressed that investigators were still not sure of why the gunman launched the attack.

Authorities have steadfastly declined to discuss a motive for the attack, saying their investigation was still underway.

Dear, a South Carolina native who appeared to have moved to a remote community in Colorado last year has been jailed ahead of a court appearance scheduled for Monday.

The shooting was believed to be the first deadly attack at an abortion provider in the United States in six years. The Colorado Springs center has been repeatedly targeted for protests by anti-abortion activists.

At least eight workers at clinics providing abortions have been killed since 1977, according to the National Abortion Federation. The most recent was in 2009 when Dr. George Tiller was shot to death at church in Wichita, Kansas.

While calling the shooting “an incredible tragedy,” Republican presidential candidate Mike Huckabee on Sunday dismissed talk that harsh anti-abortion rhetoric may have contributed to the attack.

"What he did is domestic terrorism,” the former Arkansas governor told CNN, referring to the gunman.

“There’s no excuse for killing other people, whether it’s inside ... Planned Parenthood clinics, where many millions of babies die, or whether it’s people attacking Planned Parenthood,” Huckabee said.

Abortion opponents have fiercely criticized Planned Parenthood after officials of the organization were secretly recorded by an anti-abortion group discussing compensation for providing human tissue from aborted fetuses to researchers.

Critics say the footage is evidence that Planned Parenthood illegally sells baby parts, but the non-profit organization denies the accusation, saying that a few affiliates have donated tissue for research and were paid a small fee to cover costs.

Planned Parenthood recently announced it was discontinuing the practice to tamp down the controversy, but its critics say that is an admission of guilt.

The Center for Medical Progress, which produced the videos, could not be reached for comment on Sunday but issued a short statement on its website.

"The Center for Medical Progress condemns the barbaric killing spree in Colorado Springs by a violent madman," it said.

The Colorado Springs attack led Governor John Hickenlooper to call for both sides of the debate over Planned Parenthood's activities to "tone down the rhetoric."

“I think we should have a discussion at least urging caution when we discuss some of these issues, so we don’t get people to a point of going out and committing violence,” the Democratic governor told CNN, describing the rampage as "a form of terrorism."

The national security and civil rights divisions of the U.S. Justice Department have joined state and local authorities in investigating the shooting, it said in a statement. Their participation raises the possibility that the federal government may bring a terrorism or civil rights charge, or both, against the suspect.

Two Civilian Casualties

Hickenlooper revealed that the two civilian fatalities were a man and a woman, but he offered no further information and would not say whether they were patients or employees at the clinic. Planned Parenthood said all of its employees had escaped unharmed.

Authorities have said they would reveal nothing about the pair until after their autopsy reports, likely on Monday.

Garrett Swasey, 44, the police officer killed in the attack, worked for the University of Colorado at Colorado Springs. He had joined city police in responding to reports of shots fired at the clinic. The father of two served as an elder at Hope Chapel, the church said on its website.

"We will cherish his memory, especially those times he spent tossing the football to his son and snuggling with his daughter on the couch," his wife Rachel Swasey said in a statement.

In addition to the three fatalities, nine people were injured, including five police officers.

Except for his name and age, police have only said that Dear recently resided in rural Hartsel, about 60 miles (96 km) west of Colorado Springs. Official records show that he has a history of brushes with the law, mostly in South Carolina but no criminal convictions.

One of Dear's Hartsel neighbors described the suspect as a loner who lived on his remote property with a woman. Zigmond Post Jr., said Dear once gave him a pamphlet critical of President Barack Obama but interaction between the two neighbors was limited.