Missouri officials were preparing on Tuesday to execute a man who wasn't able to appeal his conviction in federal court because his attorneys missed a filing deadline.

Mark Christeson was scheduled to die at 12:01 a.m. CDT Wednesday for the killing of a woman and her two children in 1998.

Christeson had two appeals pending with the U.S. Supreme Court on Tuesday. One challenges the state's planned use of a made-to-order execution drug produced by an unidentified compounding pharmacy. The other argues that he deserves the chance to appeal his case in federal courts, which is the norm for inmates sentenced to death.

Christeson would be the ninth person executed by Missouri this year, which would equal the state record set in 1999. That could be exceeded next month, as Leon Taylor is scheduled for execution Nov. 19 for killing a gas station attendant in suburban Kansas City 20 years ago.

In addition to the court appeals, Gov. Jay Nixon was weighing a clemency request.

In Maries County, a south-central Missouri county with just 9,000 residents, there is little argument with the death sentence, prosecutor Terry Daley Schwartze said.

"No matter how anybody feels about the death penalty, you can't find a person around here who doesn't feel it's the right result for this case," Schwartze said. "It's so very awful."

When he was 18, Christeson and his 17-year-old cousin, Jesse Carter, came up with a plan to run away from the home outside Vichy where they were living with a relative.

On Feb. 1, 1998, Christeson and Carter took shotguns and went to a home about a half-mile away where Susan Brouk, 36, lived with her 12-year-old daughter, Adrian, and 9-year-old son, Kyle. They planned to steal Brouk's Ford Bronco, Schwartze said.

The cousins tied the hands of the children with shoelaces. Christeson forced Brouk into a bedroom and raped her. When they went back into the living room, Adrian recognized Carter and said his name.

"We've got to get rid of 'em," Christeson told Carter.

Court records show that Christeson and Carter forced Brouk and the children into her Bronco and took electronics and other items. They drove to a pond.

After kicking Brouk in the ribs, Christeson cut her throat, then cut Kyle's throat and held him under the water until he drowned. Carter held Adrian while Christeson pressed on her throat until she suffocated. Carter pushed her body into the pond. With Brouk struggling to stay alive, the men tossed her into the pond, where she drowned.

Brouk's sisters discovered a few days later that Brouk and the children were missing. A Missouri State Highway Patrol helicopter spotted one of the bodies in the pond, leading to a search that found all three.

Meanwhile, Christeson and Carter drove to California, selling Brouk's household items along the way. A detective in Riverside County, California, recognized Christeson and Carter from photos police had circulated, and the men were arrested eight days after the killings.

Carter was sentenced to life in prison without parole after agreeing to testify against Christeson.