Authorities on Saturday charged Vaughn, 32, with two murder counts per victim, saying he gunned down his family in their sport utility vehicle. The killings were discovered June 14 after Vaughn flagged down a motorist on a service road in Channahon, about 40 miles southwest of Chicago.

Vaughn, who works as a computer forensic adviser, had been shot in the thigh. His wife, Kimberly, 34, was shot once, while each of their children — Abigayle, 12; Cassandra, 11; and Blake, 8 — were shot twice. His handgun was found at the scene, authorities said.

Prosecutor James Glasgow, who declined to discuss possible motives, said Vaughn was charged with two murder counts per victim. One set of counts alleges he shot with intent to kill and the other alleges he shot knowing that it was likely to cause death or great bodily harm.

Before he was arrested, Vaughn had voluntarily met with investigators three times to answer questions.

Authorities would not say what evidence tipped the balance enough to allow them to seek an arrest warrant from a judge late Friday. The charges were built from numerous interviews, forensic evidence, computer files and phone records, authorities said.

Glasgow said he has 120 days to decide whether to seek the death penalty.

"We are hopeful that with the issuance of these charges that Kimberly Vaughn and her three beautiful children can truly rest in peace," said Glasgow. "Everyone who came in contact with this case was moved by what they saw."

Word of Vaughn's arrest circulated among the mourners as the service, hundreds of miles away at New Hope Presbyterian Church in St. Charles, Mo., drew to a close.

"We should not be here today, but the events of this past week have been thrust upon us, events which are indescribable and unspeakable," said the Rev. Christopher James.

The church was a special place for Kimberly Vaughn and the children; she attended since its 1994 inception and it was the place the kids were later baptized. Kimberly Vaughn's parents still attend the church.

The service included no caskets. Kimberly Vaughn and her children had been quietly buried in a nearby cemetery to avoid media attention.

Photographs showing the kids at play or their mother's days playing volleyball filled four poster boards at the church. Only one of the roughly 100 pictures — a small snapshot of the family — showed Christopher Vaughn.

The Vaughns, who once lived in Missouri, moved from Washington state to the Chicago area about a year ago. They lived briefly in Aurora before relocating to a spacious home in Oswego.

Glasgow said he hoped Vaughn would be extradited from Missouri to Illinois soon. He said Vaughn indicated he intended to fight extradition.