LOS ANGELES (AP) _ A former firefighter faces the death penalty after being convicted of murder Friday for a hardware store fire that killed a woman, her grandson and two employees.

Investigators said John Orr set fires to develop material for a novel he was writing about an arsonist who got sexual pleasure from his crimes.

Orr, 49, was found guilty of four murder counts for the fire at Ole's Home Center in South Pasadena.

He was also convicted on several arson charges for a series of brush and house fires in the Los Angeles area in 1990 and 1991, one of which destroyed 67 hillside homes.

The penalty phase begins Tuesday.

A former captain with the Glendale Fire Department and a top arson investigator, Orr denied setting the 1984 home center fire that killed employees Carolyn Kraus, 26, and Jimmy Cetina, 17, a 52-year-old customer Ada Deal and her 3-year-old grandson Matthew Troidl.

The official probe concluded the fire was accidental, caused by an electrical malfunction in an attic. But prosecutors said the arson investigation was slipshod.

To show Orr had a motive for the fires, prosecutors entered into evidence a manuscript of a novel he wrote about a firefighter-turned-arsonist who got sexual kicks from setting fires. The book contains one chapter describing in detail a fire identical to the Ole's fire.

Orr said in letters to an agent that the book was fiction but based on ``a real arsonist.''

Orr is already serving a 30-year federal prison term for other fires. In a 1992 federal trial in Fresno, he was convicted of setting three fires in the San Joaquin Valley. The following year he pleaded guilty to setting three others. He set most of them while returning home from arson investigator conferences.