While officials have not disclosed a motive in Friday's shooting rampage at a Colorado Planned Parenthood clinic, the president of the healthcare provider's Rocky Mountains network decried "hateful rhetoric" that "breeds acts of violence."
Suspected gunman Robert Lewis Dear, 57, surrendered after a five-hour siege at the Colorado Springs clinic Friday and is being held without bond. Three people, including a police officer, were killed in the attack.
Law enforcement officials have not disclosed what motivated the attack. A federal official told NBC News it appears Dear may be mentally disturbed.
But Vicki Cowart, President and CEO of Planned Parenthood Rocky Mountains, said in a statement Saturday that witness accounts indicate it was motivated by opposition to abortion. NBC News has not confirmed those accounts.
"Today, we are learning that eyewitnesses confirm that the man who will be charged with the tragic and senseless shooting that resulted in the deaths of three people and injuries to nine others at Planned Parenthood's health center in Colorado Springs was motivated by opposition to safe and legal abortion," Cowart said.
"This is an appalling act of violence targeting access to health care and terrorizing skilled and dedicated health care professionals," she said.
U.S. Attorney General Loretta E. Lynch called the shooting rampage "a horrific attack" in a statement Saturday and said the federal government stands ready to offer any assistance it can.
"This unconscionable attack was not only a crime against the Colorado Springs community, but a crime against women receiving healthcare services at Planned Parenthood, law enforcement seeking to protect and serve, and other innocent people," Lynch said. "It was also an assault on the rule of law, and an attack on all Americans' right to safety and security."
Planned Parenthood was criticized after a series of highly-edited videos were released by an anti-abortion group earlier this year, which the group claimed showed Planned Parenthood illegally profits from selling tissue from aborted fetuses.
Planned Parenthood has strongly denied the group's claims.
"We've seen an alarming increase in hateful rhetoric and smear campaigns against abortion providers and patients over the last few months," Cowart said. "That environment breeds acts of violence. Americans reject the hatred and vitriol that fueled this tragedy."
The shootings raised fears that other Planned Parenthood facilities could be targeted. New York Gov. Andrew Cuomo on Saturday said state police have increased patrols at clinics statewide, and would meet with clinics Monday to discuss security measures.
Democratic presidential candidate Bernie Sanders affirmed his support for Planned Parenthood in a tweet Saturday and said, "I hope people realize that bitter rhetoric can have unintended consequences."
Hillary Clinton also voiced her support for Planned Parenthood, but did not mention criticism of the group. Martin O'Malley said his thoughts and prayers are with the people of Colorado.
Republican presidential candidates Ted Cruz and John Kasich offered condolences to the victims. "Senseless violence has brought tragedy to Colorado Springs," Kasich said in a tweet.