Bruce Pardo's elaborate preparations for a murderous rampage at his former inlaws' Christmas Eve party apparently included ingesting cocaine, as well as dressing in a Santa suit and fabricating a flame-accelerating device, officials said Friday.

According to an autopsy report from the Los Angeles County coroner's office, Pardo had a small amount of cocaine in his blood and urine when he killed nine people at the home of his ex-wife's parents in suburban Covina.

• Click here for photos | Click here for video.

Pardo shot himself in the mouth shortly after torching the home with his homemade device and fleeing. His badly burned body was found at his brother's home in Sylmar with part of his Santa suit melted to his leg.

Dan Anderson, a coroner's supervising criminalist, said it was impossible to determine exactly when and how the 45-year-old electrical engineer took the cocaine or whether the drug had affected his behavior in any way.

However, cocaine is a fast metabolizer, leaving the conclusion that he had taken it anywhere from 20 minutes to eight hours before his death, the toxicologist said. Any longer and traces of the drug would have disappeared from his system.

"It was a pretty small level," Anderson said. "It could exert a behavioral influence. Tolerance is everything."

Covina police Lt. Tim Doonan, who led the investigation of the massacre, said he wasn't surprised that drugs were found in Pardo's body, but police had uncovered no sign that the unemployed engineer was a drug user.

"We didn't see any indications of drug use and we thoroughly searched his house," Doonan said.

Authorities theorize that Pardo's embitterment over his recent divorce led to the bloodbath, which claimed the lives of his ex-wife, her parents, two brothers and their wives, her sister and a 17-year-old nephew. Pardo had also lost his job months earlier.

Doonan said the FBI is compiling a detailed personality profile of Pardo using extensive interviews Covina police conducted with people who knew the man, who had no criminal record or history of violence.

Such a profile may help law enforcement detect subtle warning signs that someone is ready to snap, he said.

"It's to get inside the head of somebody who was able to do something like this," he said.