Luke Helder appeared in an Iowa court Friday night to face the first of several charges that could send him to prison for life for allegedly blowing up mailboxes across the Midwest with pipe bombs.

The 21-year-old college student did not speak during the 10-minute hearing, but nodded as U.S. Magistrate John Jarvey read the criminal complaint against him.

Helder is charged in Iowa with using a pipe bomb in a crime of violence and destroying property used in interstate commerce — a mailbox. Six pipe bombs exploded in Iowa and Illinois last week, injuring four letter carriers and two residents.

Specifically, the complaint alleges Helder was responsible for the injuries suffered by Delores Werling, 70, of Tipton, Iowa. She was injured in the face, arms and hands when a pipe bomb exploded in her mailbox.

Helder was ordered held in the Linn County Jail without bail.

The judge appointed Jane Kelly, a federal public defender from Cedar Rapids, to represent Helder, and scheduled a preliminary hearing for May 22. Federal prosecutors said they would present evidence to a grand jury later this month seeking an indictment on both counts.

In all, Helder is accused of putting 18 pipe bombs and anti-government letters in mailboxes in Iowa, Illinois, Nebraska, Colorado and Texas. He told authorities after his capture Tuesday in Nevada that he wanted to create a "smiley face" pattern on the map, a sheriff said.

Helder had been flown earlier Friday from Nevada to this eastern Iowa city. His parents, Cameron and Pamela Helder of Pine Island, Minn., left Reno, Nev., on Thursday after a jailhouse visit with their son.

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

Helder, an art student at the University of Wisconsin-Stout in Menomonie, Wis., had smiled broadly each time he was transported to and from court and the Washoe County Jail in Nevada this week.

The FBI zeroed in on him as a suspect after his father called authorities about an alarming letter from his son containing anti-government statements and references to exploding mailboxes and death.