Sarah Dillon spent part of Tuesday praying at her son's gravesite, asking for a last-minute miracle.

Her desire: that the killing of her oldest son in 2002 would somehow be solved before convicted sniper John Allen Muhammad was executed in Virginia on Tuesday night. It didn't happen. Muhammad was unemotional and didn't respond when authorities asked whether he had any last words, officials said.

"I need to know something," said Dillon, 62, whose son, Billy Gene Dillon, was killed in Denton County. "I still don't know why this happened. It's very hard."

Authorities have said her son may have been among more than a dozen people whom Muhammad and Lee Boyd Malvo killed during a 2002 spree in the Washington, D.C., area and as many as nine other states, including Texas.

News reports in 2006 indicated that Malvo had told authorities that he and Muhammad were responsible for Dillon's homicide, but charges were never filed. The Denton County case remains open.

Sarah Dillon remembers the morning her son died.

She had driven him to his job doing yard work in rural Denton County one morning in May 2002, and when it started raining she returned around noon to pick him up. That's when she learned that her son had died about 10:30 a.m., apparently shot from a distance with a high-powered rifle — similar to those who were fatally shot in Washington.

Dillon wrote Muhammad and Malvo letters asking them to speak out if they indeed took her son's life. She never got an answer. "I don't think they have any remorse about them. There was something precious they took from me, " she said.

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