CONCORD, N. H. -- Hoping to "jar someone's memory" in the search for two missing children believed to have been murdered by their father, law enforcement officials Tuesday released a detailed description of the suspected burial site of Sarah Gehring, 14, and her 11-year-old brother, Philip.
The two disappeared with their father, Manuel Gehring, shortly after watching a Fourth of July fireworks display here.
The elder Gehring -- a 44-year-old unemployed accountant -- was arrested nearly a week later at a motel in Gilroy, Calif. The children were not with him, and New Hampshire Atty. Gen. Peter Heed disclosed Tuesday that the middle seat of Gehring's teal Pontiac minivan had been removed.
"Our investigation thus far leads us to believe that the seat has been deposited somewhere off I-80 in the state of Nebraska," said Heed, whose office earlier confirmed that a shovel was found in the vehicle.
Heed said investigators believe Gehring fatally shot the children somewhere near Concord "on or about July 4," and that a search for their bodies was underway "literally from one end of the country to another."
Gehring was charged late Friday with two counts of first-degree murder. If convicted, Gehring would face a mandatory sentence of life in prison without parole.
Gehring has been in police and FBI custody since he waived extradition in California on July 15. Gehring returned to Concord on Tuesday afternoon in an FBI jet. He could face arraignment as early as today, the attorney general said.
Heed said authorities know what the burial site looks like, but do not know where it is.
He said the children are believed to have been buried about 50 feet from a two-lane road somewhere off Interstate 80.
The area in question spans 700 miles, from Grove City, Pa., to Iowa City, Iowa.
But Jay Fallon, a supervisory special agent for the FBI here, said authorities have narrowed their search to a 200-mile area "at the Ohio-Indiana state border."
With large color portraits of the children behind them, the two officials offered details of the suspected grave site ranging from a "six-foot high wire fence line with a rectangular or square pattern" to an "old-fashioned hand lever-operated water pump with a chrome/silver body and a green top and green handle or lever."
Grass surrounding the suspected grave "may be 3 to 4 feet tall, green at the bottom and tan or brown at the top with seeds at the top," according to a chart posted by the officials.
The chart also mentioned cement cylinders "similar to large sewer drainage pipe sections" near where the children are thought to be buried and "an irregularly shaped cement slab ... laying flat on the ground."
Jeffrey Strelzin, an assistant attorney general here, said, "We are suggesting that the burial site is within 10 miles of Interstate 80."
But Heed merely shrugged when asked about the source of such meticulous details.
"This is what our investigation has turned up," he said. "I really can't say anything beyond that."
Investigators also displayed a map showing Gehring's path, beginning with a departure "at approximately 10:30 p.m." on July 4. Records from gas purchases, ATM withdrawals, a campsite, a corner store, a Target store and a Bank of America in San Francisco showed Gehring driving 3,200 miles across Interstates 80 and 84 before surrendering without a struggle at a Rodeway Inn in Gilroy.
The search began July 6 after the children's mother, Teresa Knight, went to Gehring's condominium to pick up her son and found no one at home. Knight told police here she had been unable to make cellphone contact with her daughter since July 4.
Sarah Gehring was a varsity cheerleader at Concord High, where a sign at the school entrance on Tuesday read, "Thoughts Are With Sarah and Philip, Family and Friends."
Her brother Philip attended a local middle school.
In addition to murder, Gehring has been charged with interference with a child custody agreement. Gehring, a native of Nicaragua who was adopted by an American family and raised in this country, was divorced from Sarah and Philip's mother.
After his former wife remarried, Gehring and Knight battled for nearly a year over a custody agreement that would allow the children to divide their time between Gehring's condominium in Concord and Knight's new home in Hillsborough, about half an hour from here.
But in court papers here, Knight -- who is pregnant with twins -- said Gehring called her days after the new accord was signed and told her he did not intend to follow it.
No one answered a phone call to Knight's house.