Robert Dear, Charged with Killing 3 and Injuring 9 Others at a Planned Parenthood Clinic in 2015, Dies in Custody By Sean Neumann

Robert Dear, the man charged in connection with a 2015 mass shooting at a Planned Parenthood clinic in Colorado, has died.

Dear, 67, died while in federal custody on Saturday, according to Federal Bureau of Prisons inmate records reviewed by PEOPLE.

The Associated Press, The New York Times, and Reuters reported that Dear, 67, died while receiving treatment at a medical facility for federal prisoners located in Springfield, Mo., on Saturday.

The outlets reported that Dear died of natural causes. A spokesperson with the Bureau of Prisons confirmed Dear’s death with PEOPLE on Wednesday but would not confirm the cause.

Dear was charged with killing three people and injuring nine others during the Nov. 27, 2015 mass shooting at a Planned Parenthood clinic in Colorado Springs, Colo., which was followed by a tense standoff with police for nearly six hours.

Police finally took Dear into custody after ramming an armored vehicle into the Planned Parenthood building in an effort to evacuate 24 others who remained inside.

Dear told police he attacked the clinic because he was “upset” at Planned Parenthood for performing abortions and “the selling of baby parts,” according to a search warrant affidavit filed in the case.

Among the victims were Army veteran Ke’Arre Stewart, 29, a father of two; Jenifer Markovsky, a 36-year-old mother of two who was accompanying friends to the clinic; and Garrett Swasey, a campus police officer who rushed to respond to the shooting after hearing about an active shooter at the clinic nearby, according to the AP.

Dear remained in custody since the day of the shooting but was repeatedly found incompetent to stand trial.

State courts in Colorado ruled him mentally unfit to stand trial in 2016 after two state-appointed psychologists diagnosed him with a paranoid delusional disorder and said he would not be able to understand the facts and reality of his case, according to the outlet.

Prosecutors then tried to convict Dear at the federal level in 2019 before a U.S. district judge again ruled the accused shooter was unfit to stand trial in 2021.