Investigators in Colorado Springs worked on Saturday to determine what prompted the shooting at a Planned Parenthood clinic that resulted in the deaths of three people, including a police officer.

Police identified the suspected gunman as 57-year-old Robert Lewis Dear, but released no other information about him. He is accused of killing two people in addition to University of Colorado Police Officer Garrett Swasey, as well as injuring at least four other officers and five more civilians.

The University of Colorado Colorado Springs said Swasey, 44, had been with the campus police department for six years and responded to the initial reports of an active shooter.

Authorities say Dear was armed with a long gun and also brought into the building several “items” that could have been explosive devices.

“We don’t have any information on this individual’s mentality, or his ideas or ideology,” Colorado Springs police Lt. Catherine Buckley told reporters, according to the Associated Press.

State investigators and federal agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives and the FBI are also involved in the investigation.

President Obama was briefed on the situation on Friday, a White House official said. On Saturday, the president released a statement noting that the gunman’s motive remains unknown, but urging the public not to let such incidents “become normal.”

“The last thing Americans should have to do, over the holidays or any day, is comfort the families of people killed by gun violence – people who woke up in the morning and bid their loved ones goodbye with no idea it would be for the last time,” the statement said.

“And yet, two days after Thanksgiving,” the statement continued, “that’s what we are forced to do again.”

While acknowledging that investigators have more to uncover, one Planned Parenthood official suggested the incident may be rooted in the “poisonous environment” that feeds domestic terrorism.

“We don’t yet know the full circumstances and motives behind this criminal action, and we don’t yet know if Planned Parenthood was in fact the target of this attack,” Vicki Cowart, president and chief executive of Planned Parenthood of the Rocky Mountains, said in a written statement. “We share the concerns of many Americans that extremists are creating a poisonous environment that feeds domestic terrorism in this country. We will never back away from providing care in a safe, supportive environment that millions of people rely on and trust.”

U.S. Rep. Chellie Pingree, D-Maine, referred to Friday’s shootings as “another vicious and violent attack on women’s health care.”

“The only person responsible for these attacks is the shooter who entered that clinic. But the recent smear campaign and systematic political attacks on Planned Parenthood have created an environment that could encourage deranged individuals to carry out violent attacks like the one that happened yesterday,” Pingree said in a written statement.

The shooting occurred during a period of heightened scrutiny for Planned Parenthood. In July, an anti-abortion group released a series of secretly filmed videos from a clinic in Denver that showed staffers discussing the extraction of fecal tissue from aborted fetuses before that tissue is sent to research facilities. Planned Parenthood officials have said the videos were heavily edited to bolster critics’ false claims.