A man charged in a truck bombing Wednesday was likely nearby when 11-year-old Adam Cook climbed into the truck moments before the bomb was detonated, critically injuring the youth.

The bomb was apparently detonated by remote control, according to a complaint filed in U.S. District Court Friday.The complaint charges Steven Douglas Thurman, 32, 3843 W. 3390 South, with possessing an unregistered destructive device. Thurman told federal investigators he decided to make a bomb a month ago, the complaint says.

The apparent motive for the bombing: jealousy. The child's father, Howard Cook, had begun an affair with Thurman's wife, Wendy, while both men were still married to their respective spouses, according to a complaint filed in U.S. District Court Friday. Each man is now divorced.

Thurman was arraigned in federal court late Friday on the charge, which carries a maximum 10-year prison sentence and a $250,000 fine.

State charges over Adam Cook's injuries are pending.

The child remains in critical and unstable condition at University Hospital with severe head injuries.

The investigation focused on Steve Thurman hours after a pipe bomb loaded with nails exploded in Cook's Landcruiser at 9:30 Wednesday night while it was parked in front of a Murray residence.

Cook and his two sons were visiting a friend who lives at 5740 S. 665 West. The truck was parked in front of the house. The Cooks were getting ready to leave and Adam had gone out to the truck to wait for his father and brother when the bomb exploded.

The 12-inch pipe bomb contained batteries, black powder and a remote-control receiver, the complaint says. The pipe - 2 3/8 inches in diameter - was wrapped in three different sizes of nails.

The explosion left a AA size battery lodged behind Adam's eye, requiring emergency surgery to save his life, the complaint states.

Investigators interviewed Howard Cook in the emergency room of the University Hospital the night of the bombing. Asked if he knew anyone who might want to hurt him, Cook told the investigators about his affair with Wendy Thurman and fingered Steve Thurman as a possible enemy.

Diane Burbidge, a neighbor of the man the Cooks were visiting when the bomb went off, saw a car like Thurman's drive away as soon as the bomb exploded.

After Burbidge heard the explosion, she looked out her window and saw a small, light-colored, two-door car leave the area, going fast with its lights out, the complaint states.

The affair between Howard Cook and Wendy Thurman apparently began when the couple met at work. Both work for Metz Baking Co, 3475 S. 300 West. An anonymous caller phoned in a bomb threat to the bakery on Tuesday, the day before the bombing of Cook's truck.

The couple's affair continued through the divorces of both the Cooks and Thurmans, the complaint said. Marian Cook, Howard's ex-wife, told federal investigators that Howard's affair contributed to the couple's January divorce, the complaint states. She learned of the affair when Steve Thurman called to tell her.

Linda Mae Bird, Steve Thurman's aunt, told investigators "Steve was extremely angry at Wendy because of the divorce and that he hates Wendy for it," the complaint says.

She said Steve told her six months ago that he hired a private investigator to watch Howard Cook and Wendy Thurman. She said, "Steve knew where Howard parked his Landcruiser when he was visiting Wendy at her residence and he had photos of them together."

Howard Cook told investigators he spend Tuesday night - the night before the bombing - at Wendy Thurman's house.

Federal and local law enforcement officers obtained a "no knock" search warrant and went to Steve Thurman's apartment at 5:30 a.m. Friday. Investigators kicked in the door and searched the apartment.

The search of the apartment, plus a search of Steve Thurman's vehicles and and a Midvale storage unit, revealed three different kinds of nails identical to those wrapped around the bomb; duct tape identical to the tape used to wrap the nails around the pipe; a bench vise and pipe wrench both opened to the approximate diameter of the bomb; five screws of the unusual kind used in remote-control devices, black powder and wire, the complaint says.

Neighbors characterized Steve Thurman as a quiet, "mellow" man. A woman who lives upstairs from him said he had never indicated to his neighbors that he was upset about his divorce.

Steve Thurman is a slight, sandy-haired man with a ruddy complexion and muscular build. He refused to look at his terminally ill mother during his appearance in court Friday afternoon. His face showed no expression as he listened to U.S. Magistrate Ronald Boyce read the complaint against him, including the details of Adam Cook's injuries. He silently read along from his own copy of the complaint and later used the complaint to shield his face as he left the federal courthouse.

But that complaint reveals a series of tragedies in Steve Thurman's life.

His father committed suicide while Steve Thurman was in his teens. His mother is now dying of cancer. He was laid off at Hercules a few months ago and hasn't been able to find a job since.

Boyce will hold a hearing at 11:30 a.m. Monday to determine if Thurman should be released on bail or held in the Salt Lake County Jail until his trial.

Deseret News staff writer Patty Henetz contributed to this report.