The 21-year-old college art student accused of putting pipe bombs in mailboxes in five states told authorities he was trying to make a "smiley face" pattern on the map, a sheriff said Thursday.

The first 16 bombs were arranged in two circles, one in Illinois and Iowa and the other in Nebraska. On a map, the circles could resemble the eyes of the popular 1970s happiness symbol. The final two bombs, found in Colorado and Texas, form an arc that could be the beginning of a smile.

"There was a comment made to one of my officers about his hope to make a smiley face when he was all finished," Pershing County Sheriff Ron Skinner said.

Skinner said Luke Helder made the comments to an undercover county officer shortly after his arrest outside Reno on Tuesday.

"His demeanor was very jovial. He didn't seem to be taking anything seriously at the time," the sheriff said.

An FBI official would not comment on the sheriff's report.

Meanwhile, Helder's parents, Cameron and Pamela Helder, met with their son at the county jail in Reno for a half-hour. They were separated by glass and spoke by telephone.

"We are here to see our son in his hour of need," Cameron Helder told reporters afterward. "We told him we love him. I feel a lot better after speaking to him."

Helder faces federal charges in Illinois, Nebraska and Iowa, where he will be taken Friday for an initial court appearance. U.S. Magistrate Robert McQuaid Jr. denied a request Wednesday to release Helder to the custody of his parents.

"It's apparent to me that he suffers from some apparent mental health problems," McQuaid said.

If convicted, Helder could be sent to prison for life. Cameron Helder said he expects the legal proceedings to be a long process.

"It's already been very hard on us," he said. "Our heart goes out to the families of the victims."

The FBI said Helder placed 18 pipe bombs in mailboxes in Iowa, Illinois, Nebraska, Colorado and Texas, along with anti-government notes. Six of the bombs exploded last Friday, injuring four letter carriers and two residents.

The eight bombs in Iowa and Illinois were found in rural locations that form an uneven ring about 70 miles in diameter. The Nebraska bomb sites — about 350 miles away — form a ring about 90 miles across.

The other bombs were found hundreds of miles away — one in Salida, Colo., the other in Amarillo, Texas.

The FBI issued an alert for Helder after his father called police Monday night about letters from his son that included references to death, anti-government comments and the phrase "Mailboxes are exploding." The same phrase was in the notes found with the bombs.

Authorities said Luke Helder has confessed to making 24 pipe bombs out of smokeless gunpowder, BBs or nails, paper clips and Christmas tree bulbs. The final 10 bombs found in mailboxes and the six found in his car had different detonation mechanisms and were not rigged to explode but were still dangerous, authorities said.

"Same pipe bombs, but he did not hook the battery to them," said Terry Hulse, the FBI agent in charge in Las Vegas. "The difference is when people opened the mailbox, they found them laying there."

Helder's parents arrived at Reno-Tahoe International Airport early Thursday from their home in Pine Island, Minn.

Cameron Helder said he wanted to thank the FBI and the sheriff's department for making the visit possible "so we have a better understanding of what is going through his mind and what is happening."

Helder wore a broad smile each time he was transported to and from jail and court. Washoe County Sheriff Dennis Balaam said Helder did not seem upset that his father had turned him in.

"I think he understands. I don't think there are any ill feelings there at all," the sheriff said. "It was an emotional goodbye. It's a difficult time for all."

The sheriff added: "I think as each moment goes by the consequences are starting to set in with him."

Balaam also said Helder, a junior art and industrial design major at the University of Wisconsin-Stout, was headed for California when he was arrested. Balaam said he did not know why.

Elsewhere Thursday, authorities in Sioux City, Iowa, blew up a pipe with no explosives found by three young boys and three small bombs made with drain cleaner exploded in mailboxes north of Spokane, Wash. There were no injuries in either case.

Indiana State Police also said that at least two juveniles are suspected of planting two pipe bombs in roadside mailboxes earlier this week. One of the bombs exploded, but there were no injuries.