Independence, Mo. ? More than three years after his children disappeared, Dan Porter was charged Tuesday with their slayings, telling reporters that he had confessed and was still haunted by their deaths.

“I can’t get them out of my mind,” Porter, his voice breaking, said while sitting in a sheriff’s van.

His comments came shortly after his first court appearance on two counts of first-degree murder in the shootings of his son, Sam, 7, and daughter, Lindsey, 8.

Porter, 44, already was serving a 38-year prison term for kidnapping the children to terrorize their mother, Tina Porter. When the children’s remains were found in September in a wooded area in Sugar Creek, Sam and Lindsey had been missing since June 2004, after Porter picked them up from their mother’s Independence home for a weekend visit.

“I’m sorry,” Porter told reporters. “No matter how sorry I am, I realize there are going to be people who never forgive me.”

Asked why he did it, Porter said: “Could any man come up with an excuse for that? Is there such an excuse?”

As he was led to the van that would take him back to jail, Porter, wearing an orange prison jumpsuit and shackled at his wrists and ankles, acknowledged that he had confessed to the killings. Asked why he waited so long, Porter said: “I couldn’t take it no more.”

During Tuesday’s hearing, a judge read the charges, and not-guilty pleas were entered for Porter.

A preliminary hearing was set for Dec. 19.

Porter did not have an attorney at the hearing, but public defender Timothy Burdick was assigned to him afterward. Burdick did not return phone or e-mail messages seeking comment.

According to the probable cause statement filed with the charges, the children’s remains were found after Porter met with FBI agents and Missouri Department of Corrections officials on Sept. 7 and confessed that he killed his children the day he had picked them up for the visit. The documents also say Porter led agents to the spot where the children were killed and buried.

According to the court documents, Porter told authorities he had been planning to kill his children since two days before their visit.

Jackson County prosecutor Jim Kanatzar said he would decide within the next month whether to seek the death penalty. He said capital punishment was being considered because of the circumstances of the crime.

“All cases involving children are horrific. This one particularly struck a chord because of the ages of the children and the fact that the defendant was their father. It’s a terrible case,” Kanatzar said during a news conference.

He said the children were killed with a handgun but could not provide additional details about the crime, including why Porter finally confessed.

“There is absolutely no explanation for actions like this,” he said.

After his arrest on the kidnapping charges, Porter told authorities several stories about what he had done with his children, including that he had cut them up and that he had strangled them.