A Laurel man who told authorities that an armed hitchhiker abducted his two children during an altercation on a bridge over the Choptank River was arrested here today and charged with shooting to death his 2-year-old son and critically wounding his 3-year-old daughter.

Police said the man, Richard W. Spicknall II, shot the children and then staged the carjacking.

The children, still strapped in their car seats in the locked Jeep Wrangler their father had been driving, were found about 7:45 this morning less than a half-mile from the Frederick C. Malkus Jr. Memorial Bridge by construction workers arriving at the site of an unfinished home, authorities said.

Sources said that troopers who went to the house where the Jeep was found tried to revive both children. The boy, Richard Spicknall III, was pronounced dead at Dorchester County Hospital, doctors and police said.

The girl, Destiny Array Spicknall, was resuscitated at the hospital, underwent unspecified surgery there and then was flown this afternoon to the University of Maryland Medical Center in Baltimore, where she was listed in critical condition tonight. A doctor who treated the child said, "It's going to be a long road until we have an outcome."

Richard Spicknall II, 27, was charged with first-degree murder, attempted murder, first-degree assault and a handgun count, state police spokesman Maj. Greg Shipley said. Shipley, who declined to say how many times the children were shot, said that the gun had not been recovered.

Dozens of police cadets searched the bridge today for evidence, and sources said that police divers will search the Choptank tomorrow for the handgun used to shoot the children.

Police provided few details about what might have prompted Spicknall, former manager of the ESPN Zone sports bar in Baltimore, to attack his children. They said they believe that the children were shot in Talbot County but were still investigating.

"We obviously don't believe his original story," Shipley said of Spicknall. Sources said authorities immediately doubted that a father driving his children late at night would have stopped to pick up a hitchhiker.

Shipley declined to say what Spicknall told authorities during 18 hours he spent in police custody.

Spicknall appeared here tonight before a District Court commissioner, who ordered him held without bond.

As 10 reporters crowded into the small hearing room, Commissioner Sue Shortall asked a number of routine questions, including: "Number of dependents?"

Spicknall was silent for a moment, then replied quietly, "Two," paused and said: "One. I don't know," and shook his head.

He said he is currently unemployed.

Police were dispatched to secure the Glen Burnie home of Spicknall's parents, which authorities said Spicknall "frequented."

Spicknall and his wife, Lisa Marie, were in the process of divorcing and shared custody of the children, according to a July 19 consent agreement filed in Howard County Circuit Court. According to the agreement, Richard Spicknall was to have custody of the children from 8 p.m. Sundays to 8 a.m. Wednesdays.

Cheryl Romey, of Brooklyn Park, Md., Spicknall's maternal aunt, was among the relatives who gathered outside the family home tonight. She said that her nephew, who is called "Wayne" by family members, had made special arrangements to have the children this week so they could join other family members in Ocean City, Md., for a vacation.

She said she did not believe that her nephew harmed the children.

"He did not harm that baby at all," she said. "I've watched him pick up those kids. He loves those kids."

Other relatives were at the police barracks here. Romey said that Spicknall's mother was among them.

"Right now, his mother is hysterical," Romey said. "She is so upset she can barely talk."

Court records show that Lisa Marie Spicknall filed for divorce in December after a November altercation during which Richard Spicknall allegedly told her to leave, then shoved her against a wall and threw her clothes on the floor.

Lisa Marie Spicknall was at the hospital with her daughter tonight and could not be reached for comment.

The first 911 call that alerted authorities came at 2:51 a.m. from a pay phone at a fishing pier, investigators said. It was from a bystander, who said he heard someone calling for help from the water. The state Department of Natural Resources police were alerted for a possible water rescue. State police responded after a second 911 call at 3:01 a.m. from someone who said a man claimed to have been carjacked and thrown from the bridge.

Richard Spicknall told police that a hitchhiker he had stopped to help about 11 p.m. last night confronted him with a gun, pushed him off the Malkus Bridge and then escaped with his Jeep, the children still inside.

The bridge, which straddles the Talbot-Dorchester county line, is about 90 miles from Washington and about halfway to Ocean City.

Spicknall told police that he swam to the pier to call 911 for help, but authorities said the first 911 call came more than three hours after Spicknall said the carjacking had occurred.

Witnesses told police that they saw Spicknall emerge from the waters of the Choptank River within sight of the house where the children were discovered later.

Tony Van Dyke, 40, who lives on a sailboat on the Choptank River, said in an interview today that he and his wife drove across the Malkus Bridge between 11 and 11:15 p.m. Wednesday and saw that the opposite shoreline was lit up with emergency lights of police and firefighters, who were responding to a small fire in the Cambridge visitors center.

The couple wondered why Spicknall would go to the dark end of the bridge when emergency officials were clearly on the other side.

About 4 p.m. today, Lisa Marie Spicknall and her mother arrived at the Easton state police barracks carrying small blankets. They ducked their heads and were ushered in by police.

A short time later, Richard Spicknall -- handcuffed and dressed in green sweat pants, a baggy, forest-green T-shirt and white tennis shoes -- was placed in a light blue Quest minivan and driven 12 miles south to the bridge, then the fishing pier and finally to the house where the children were found.

Charging documents said that Spicknall had given a statement about the shootings and that he had purchased a 9mm Smith & Wesson handgun Sept. 2 from a pawnbroker in College Park.

Even before Spicknall was charged, his story of a carjacking provoked more suspicion than sympathy in Cambridge, a graceful waterfront town of turn-of-the-century buildings and about 12,000 residents.

"It's something crooked. He didn't get 'jacked," said the proprietor of an auto body shop near the bridge who declined to give his name.

Skeptical residents were quick to poke holes in the emerging account, noting the height of the bridge (about 50 feet at its highest point), the Choptank's strong and dangerous current (which presumably would have swept Spicknall in the opposite direction of where he supposedly emerged from the water east of the bridge) and the scarcity of pedestrians or hitchhikers on the bridge.

Many said they were quickly reminded of the case of Susan Smith, the South Carolina mother who in 1994 maintained for days that a carjacker sped off with her two young sons before finally acknowledging that she had drowned them in her car.

"Nowadays you have to take the whole world as a lie and then find out the truth," said Jennifer Cannon, 20, a nursing assistant who waited for an appointment at a beauty salon near the bridge. "If I had my son in the back seat, I'm not going to stop to pick up some stranger and have him sit back there with my son."

Staff writer Raja Mishra and Metro staff researcher Bobbye Pratt contributed to this report.