Mitchell Johnson, who as a teen helped shoot and kill five people in a schoolyard ambush in Jonesboro, was sentenced Thursday to four years in prison on an unrelated federal weapons charge.

U.S. District Judge Jimm Larry Hendren also added three years of supervised release to the sentence, during which Johnson must meet certain conditions, such as submitting to drug testing.

Hendren expressed dismay that Johnson had not taken advantage of the chance at a new life afforded him upon his release after years in custody for the Jonesboro shootings.

While his trial contained no reference to the 1998 shooting at Jonesboro's Westside Middle School, it weighed heavily on Johnson's sentencing hearing Thursday. Prosecutors argued Johnson should serve more time as federal guidelines did not take into account the severity of the shootings, which left five dead and 10 others wounded.

"No matter what I do today, you will have a life to live," the judge said. "Those who died in 1998 will not."

Johnson had faced a maximum sentence of 10 years in prison and a $250,000 fine after being convicted in January of possessing a firearm while being a user of or addicted to a controlled substance.

Johnson already was being held at the Benton County jail on separate state charges, accused of taking a debit card left by a disabled man at the Bentonville gas station where Johnson worked. At his sentencing, Johnson wore black-and-white-striped prison clothes, his white socks visible through jail-issued sandals.

Johnson rocked back and forth in his chair, his hand clasped in his lap. When asked if he had a statement, Johnson told the Fayetteville courtroom that "not a day goes by that I don't think about what happened" — nearly the same comments he made to Washington County deputies who arrested him Jan. 1, 2007.

During the hearing, which lasted nearly three hours, Assistant U.S. Attorney Candace Taylor argued for an upward revision in federal sentencing guidelines, saying the standard calculation, which takes into account prior criminal sentences, didn't adequately account for the seriousness of Johnson's 1998 conviction because he was a juvenile at the time. The calculation called for a sentence of no more than two years.

Johnson's lawyer, Jack Schisler, argued that the guideline sentence was adequate. To go beyond it, he said, would amount to "re-sentencing" Johnson for the 1998 crimes.

Judge Hendren, however, agreed with the prosecution's proposed range of 41 to 51 months. He said the fact that Johnson was found in possession of firearms, despite the shootings of a decade ago, was "very, very worrisome."

When Johnson was arrested during the 2007 traffic stop, he was traveling with Justin Trammell, who had been found delinquent after shooting his father to death with a crossbow in 1999. Johnson and Trammell were roommates.

Deputies had received a tip the duo's van carried 100 pounds of marijuana. Deputies found only 21 grams of the drug but also found a nickel-plated handgun and a 20-gauge shotgun. State prosecutors later turned the case over to federal prosecutors.

In 1998, Johnson and classmate Andrew Golden stole guns from Golden's grandfather and a white van belonging to Johnson's stepfather. They waited in camouflage atop a wooded hill after Golden triggered a fake fire alarm.

They opened fire as classmates and teachers left the school. Shannon Wright, an English teacher, died while shielding student Emma Pittman from a pair of bullets. Students Natalie Brooks, 11; Paige Herring, 12; Stephanie Johnson, 12; and Britthney Varner, 11, all died of their wounds.

The federal government had held Johnson and Golden until age 21 after the Jonesboro shootings. At the time of the schoolyard massacre, Arkansas had the means only to hold Johnson and Golden until age 18.

After his release, Johnson spent time in several states before returning to Arkansas to work at a Wal-Mart. The night of his traffic-stop arrest, he told deputies he planned on moving to California to start his life over.