Sean Janssen, The Union Democrat

Whatever Philip Marshall did, he never seemed to do it halfway.

The 54-year-old Murphys pilot, author and former Little League coach went to great lengths in devotion to causes that inspired passion in him. In recent years, that meant an investigation of the 9-11 terrorist attacks and a campaign to end a suspension of his favorite pro-football team's head coach that garnered national attention.

No one who knew him got any impression he was capable of shooting and killing his own two teenaged children late last week before turning the gun on himself.

No note or any explanation for the brutal crime could be found when investigators visited the crime scene during the weekend, Calaveras County Sheriff's Office spokesman Sgt. Chris Hewitt said.

"Foul play by outside persons has been ruled out," Hewitt added, "and evidence at the scene confirmed that Philip Marshall was the shooter."

Calaveras County Coroner Kevin Raggio confirmed Monday that Marshall and son Alex, 17, and daughter Macaila, 14, each died as a result of a single gunshot wound to the head.

Raggio said a full autopsy is scheduled today, but he does not expect the results to reveal much more than that.

"In 28 years (as a funeral home director), 11 or 12 as the coroner, I've never seen anything like this," Raggio said. "This kind of thing happens someplace else. You don't expect this kind of thing to happen here."

The autopsy will likely give a better indication of when the deaths occurred. The shootings are believed to have occurred sometime between late Thursday and their discovery Saturday afternoon by friends of the Marshall siblings.

Hewitt said the 9mm Glock semiautomatic pistol used by Marshall is legal to own in California. Investigators as of Monday hadn't been able to determine if it was registered to him.

An initial statement from the Sheriff's Office indicated Marshall had no prior contact with law enforcement.

However, Hewitt said further research Monday showed he had been arrested on Dec. 5, 2008, for suspicion of battery, disturbing the peace and making annoying or threatening phone calls. No charges were filed in the case, which stemmed from a call made to police by Marshall's estranged wife, Sean, and her sister, Erin Chamberlain, of Murphys.

According to police reports, Philip became involved in an argument with Chamberlain outside of Sean's home on the 100 block of Fieldstone Drive in Murphys. The argument stemmed from Philip wanting to see Macaila. During the argument, he allegedly slapped Chamberlain in the face. Hewitt said charges were not filed ultimately "due to credibility issues with witnesses."

Four weeks earlier, on Nov. 8, Philip called police to allege Sean had burglarized his home and taken prescription medications.

She was arrested for suspicion of first-degree burglary and possession of drugs without a required prescription. Information on what that medication was specifically, whether charges were filed and the outcome of the case were not immediately available Monday.

Calaveras County Superior Court documents indicated the Marshalls separated in 2008 and Sean moved out of the couple's Forest Meadows home, where the deaths occurred. She later moved to the Fieldstone home, spent time in Santa Barbara and later relocated to Angels Camp.

She filed for divorce on Oct. 15, 2012, citing irreconcilable differences and petitioned for joint custody. Philip Marshall had not responded to his wife's filing at the time of his death. A hearing on the matter had been scheduled for Feb. 25 in the Calaveras County Superior Court.

Philip Marshall gained some attention for his decade-long investigation of the Sept. 11 tragedy. He wrote a book, "The Big Bamboozle," with editions published through a small publishing house known as Pleasant Mount Press and CreateSpace, an outfit that assists self-publishers.

Marshall touted his experience flying commercial jetliners. He claimed to have worked as a "contract pilot" for covert CIA operations during the Iran-Contra scandal to boost his credibility. He appeared in podcast interviews with hosts willing to provide a forum for his conclusions that American and Saudi governments secretly planned the 9-11 attacks.

A columnist for the weekly Santa Barbara Independent interviewed Marshall in September and wrote that he "can't get a nibble" on the 9/11 theories, particularly compared with the relative success of his "Free Sean Payton" campaign.

In various interviews, Marshall indicated he felt Payton, head coach of his beloved New Orleans Saints, got a bum rap from NFL Commissioner Roger Goodell, who suspended him for the season in relation to a controversial "bounty system" that encouraged Saints players to injure their opponents.

Though it had been several years since Marshall flew for United Airlines, FAA records show he maintained his pilot's license. He took to a private plane in August and September to fly over the Saints' practice field as well as MetLife Stadium in East Rutherford, N.J., home to the NFL's New York Giants and Jets.

Marshall's plane carried a banner with the "Free Sean Payton" message in each case. New Orleans' WWL Radio reported the flight plan for the MetLife fly-over would take him over the Statue of Liberty, Manhattan and the Hudson River. The route also would have provided a bird's eye view of Ground Zero.

His passion for the Saints began when he attended the club's inaugural game in 1967 with his father, WWL reported.

Though many sympathetic NFL fans seemed to agree with Marshall's anti-authority message in the Payton affair, it ultimately fell on deaf ears. The league did not reinstate the coach until Jan. 23, about a week before Marshall's anger tragically turned on his family.