A security guard accused of burning down homes at the suburban Washington housing development where he worked told investigators he was upset his employer did not show enough sympathy after his infant son died this year.

Aaron L. Speed (search), 21, who worked for Security Services of America, told police he left his job from August to October because of SSA's "indifference to the death of his infant son," according to court papers released Friday.

When asked by investigators who might have started the fire, Speed said: "Someone who works at the site and recently experienced a great loss."

A relative said Speed lost an infant son earlier this year.

"He was devastated," said Debbie Leman, a bartender at a tavern frequented by the family. "The only thing he cared about was his kids."

Speed had been hired to protect the Hunters Brooke (search) development, where a string of fires Dec. 6 destroyed 10 houses and damaged 16 others. Authorities said it was the biggest residential arson case in Maryland history, with damage put at $10 million. No one was hurt in the fires; many of the houses were under construction.

Early on, there was speculation the fires were set by environmental extremists (search), because some environmental groups had complained that the houses were a threat to a nearby bog. But no evidence has been found to support that theory, police said.

According to an affidavit, Speed told authorities "that he was present at the location, along with others with whom he was acquainted, while the fires were being lit," according to an affidavit.

"Speed claimed that he knew of the plan by others known to him to set a fire at the location," the affidavit continued. "He also asserted that he told others how to gain access to the site."

Speed made the statements after failing a polygraph test (search) Thursday, when he was arrested on arson charges. On Friday, he was ordered held until a hearing next week.

According to court documents, Speed allegedly told investigators he was home in bed when a colleague phoned to tell him of the fires; records obtained from his cell phone service showed the call went through a cell phone tower closer to the scene.

The scale of the arson — the fires broke out almost simultaneously — has led investigators to believe that more than one person may have been responsible. Authorities believe the fires were set using an accelerant and a propane torch.

Speed's attorney, John Chamble, declined to comment.

Linda Auwers, general counsel for the parent company of SSA, said only: "We are fully cooperating with the authorities in their investigation of this matter."

Speed told WUSA-TV outside his parents' home Thursday that police have the wrong man: "Everything that I'm doing, I'm doing willingly to prove to them that I am innocent."

Authorities searched the home of Speed's parents on Wednesday night and towed a car away, said David Jaillet, whose stepdaughter is Speed's wife. Jaillet said the couple married about a year ago and had twin boys earlier this year, but one of the boys died of intestinal complications.

The suspect's former foster mother, Faith Kern, said Speed was "overcoming his anger" while he lived with her when he was 19; she declined to say why he left his mother and stepfather's home.

"He has overcome some difficulties in his life, but he made progress with me," she said. "I found him to be a very likable person."