The 34-year-old officer from the Marana Police Department, a suburb north of Tucson, told an investigator he had considered shooting the suspect but that doing so would put other officers and bystanders at risk.
The interview was released to The Associated Press on Friday after a public records request.
Rapiejko is calm and detailed as he explains his thinking and actions that day.
He had rammed his police cruiser into 36-year-old Mario Valencia, who police say had stolen a rifle before threatening to kill himself and shooting it in the air next to another police officer. The encounter was captured on two dash-cam videos that police released to the public this week. The videos went viral and drew international attention at a time when police actions are under scrutiny.
Rapiejko told the investigator he had first instructed dispatchers to tell nearby businesses to lock down. When he learned that Valencia was refusing to obey police orders and kept walking toward a business, he decided the situation merited deadly force.
"I have two thoughts going through my mind. I need to shoot him to stop the threat, or I need to run him over to stop the threat," Rapiejko said.
But he was too far -- about 50 yards away -- to shoot accurately with a handgun, a less powerful weapon than a rifle, which has a longer range.
"So (because of) the potential for really bad collateral damage if I missed that shot in terms of priority of life and innocent bystanders, or one of us, I decided that was not an option," he said. "I wanted to stop the threat. That was the only thing on my mind."
Marana police say Rapiejko is a hero for preventing a potentially deadly situation. The Pima County Attorney's Office has declined to file charges against him, saying there was insufficient evidence to prove Rapiejko had criminal intent when he struck Valencia.
Valencia's lawyer called Rapiejko's actions excessive and unjustified.
"In watching the video, I think it was clear that it was not the appropriate action and that my client was not threatening to anybody except for himself," Michelle Cohen Metzger said Wednesday.
Policing experts say Rapiejko's use of his patrol car to stop Valencia was unconventional and even outrageous, but justified because of the danger Valencia posed to officers and others around him.
Rapiejko, who previously worked for the New York City and Tucson police departments, has been with Marana since early last year.
He has been previously accused of using excessive force in a lawsuit that resulted in a $20,000 settlement from New York City to Luis Colon, a man who accused Rapiejko of pointing a gun at him and choking him during a 2005 encounter.
Marana police Sgt. Chris Warren said that New York Police Department internal affairs and a citizen review panel cleared Rapiejko of any wrongdoing and that Marana police knew of the incident but didn't find merit to it.
Rapiejko was back on the force after a standard three-day administrative leave following the incident.