Sean Janssen, The Union Democrat

It may be impossible to know why Philip Marshall killed his own two children last week.

Autopsies completed Tuesday on the 54-year-old author and pilot, son Alex, 17, and daughter Macaila, 14, revealed no new information, according to a spokesman for the Calaveras County Coroner's Office.

The preliminary finding of single gunshots to the head in each case held up as a cause of death.

It could not be determined precisely when the deaths occurred. The children sent out text messages late Thursday night, but the grisly scene at their Forest Meadows home was not discovered until Saturday afternoon.

The time of the discovery, 3 p.m. Saturday, will be listed as the official time of death.

A toxicology screen of Philip Marshall will be conducted and results are expected in four to six weeks.

Calaveras County Sheriff's Office investigators did not find any sort of note at the home and none could be found on the person of Philip Marshall or his victims before the autopsy.

Sheriff's Sgt. Chris Hewitt said Tuesday that investigators did determine the 9mm Glock semiautomatic handgun used in the crime had been registered to Philip Marshall.

In many regards, Marshall fit the profile for the perpetrator of a murder-suicide.

In a recent study, Johns Hopkins University researcher Jacquelyn Campbell found that 70 percent of such cases occurring throughout 12 U.S. cities were preceded by domestic violence.

Ninety-one percent of perpetrators were men, 88 percent used a gun and most were white, according to Campbell's research.

Custody battles, financial collapse and deteriorating physical or mental health are common factors in this type of crime, wrote Richard Gelles, professor and dean of the School of Social Policy and Practice at the University of Pennsylvania, in an email Tuesday.

"My quick read (of news clips) and my experience suggests he might have been in a downward spiral of mental illness," Gelles said.

Hewitt said any information on Marshall's mental health revealed in the investigation will not be released, nor could he say whether any medications were discovered at the home.

A report of domestic violence involving Marshall was made in December 2008.

He allegedly slapped Erin Chamberlain, the sister of his estranged wife, Sean Marshall, in the face during an argument with both women about custody of Macaila.

Philip Marshall was arrested and briefly taken into custody but no charges were filed.

About a month before that incident, on Nov. 11, 2008, Philip Marshall called police to allege his wife had illegally entered his Forest Meadows home two months after their separation earlier that year and taken pills for which she did not have a prescription.

Court records state Marshall told a deputy who responded that afternoon that Sean Marshall entered the house "while he was hiding in the shower with a video camera."

He told police she went straight for a bottle of six 20-milligram pills of Kadian, an extended-release morphine medication prescribed for patients who have shown a tolerance for similar opioid painkillers.

During the response, Sean Marshall drove up and was arrested, the records stated.

She told police she took the pills and hid them in a tree so she could give them to her lawyer.

The Calaveras County District Attorney's Office charged Sean Marshall with petty theft, trespassing and possession of drugs without a prescription.

Court records show the case continued in the Calaveras County Superior Court while she attended Alcoholics Anonymous and/or Narcotics Anonymous meetings. After providing an attendance card at a Sept. 28, 2009, hearing, all charges against her were dismissed.

Sean Marshall filed for a divorce from her estranged husband in October 2012 with no hearings set in the case until Feb. 25.

Statistics show murder-suicides most often target the perpetrator's spouse as a victim. Sean Marshall had been traveling in Turkey when notified of the loss, according to a Sheriff's Office statement.

"Some of these murder suicides are designed to punish the other spouse," Gelles noted, even if that person is not killed.

Financial troubles do not appear to be a factor. According to county records, the Sandalwood Drive home where Philip Marshall resided was not in foreclosure and taxes were current on the property. The house was refinanced in July, and the couple had taken out a $235,000 home equity loan in 2006.

Philip Marshall had been a commercial pilot for about 20 years before leaving that career for unknown reasons. He published several books claiming to have flown as a contract pilot for the CIA and Drug Enforcement Agency and to have uncovered a Saudi-American plot to perpetrate the terrorist attacks of Sept. 11, 2001.

"We're unaware of any information that would substantiate Mr. Marshall's claims," CIA spokesman Preston Golson wrote in an email Tuesday.

Hewitt said the investigation conclusively showed Philip Marshall as the shooter, but that he could not reveal any further details in that regard.

Whether the full details of the crime are ever revealed or not, those who sympathize with Marshall's theories about a malicious covert government will likely never be satisfied.

By Tuesday afternoon, numerous websites were positing theories and hosting anonymous posts suggesting that covert operatives were to blame for the tragic loss of life that struck a quiet community.

Those grieving locally were finding more productive ways this week to remember Alex and Macaila Marshall.

A candlelight vigil is scheduled for 7 p.m. today on the quad at Bret Harte High School.

A bereavement fund for the siblings has been set up at the U.S. Bank branch in Angels Camp. Donations can be made out to Alex and Macaila and mailed to the bank at 580 S. Main St., Angels Camp, CA 95222. The donations will go toward the memorials and a student annual scholarship for Bret Harte High School.

The funding will consider students who are involved with the promotion of mental health awareness and gun control regulations in the community, according to organizers.

Donations to the bereavement fund will be accepted in lieu of an entry fee at a dance scheduled to follow the Bret Harte-Calaveras basketball game Friday at Bret Harte High School.

For more information about the fund, call Veronica Stow at 530-574-1129.