WASHINGTON (AP) — More than 500 gun purchases have been blocked since a new gun law requiring stricter background checks for young people went into effect in 2022, Attorney General Merrick Garland said Friday, the day after a school shooting in Iowa left a sixth-grader dead.

The bipartisan law passed in June 2022 was the most sweeping gun legislation in decades and requires extra checks for any gun purchases by people under age 21. Those denied a gun purchase include a person convicted of rape, a suspect in an attempted murder case and someone who had been involuntarily committed for mental-health treatment, according to the Justice Department.

President Joe Biden applauded the news, calling it an important milestone.

"Simply put: this legislation is saving lives," Biden said in a statement where he also called for additional measures such as universal background checks and a ban on firearms often referred to as assault weapons. The Democratic president said he was "proud to have taken more executive action than any president in history to combat gun violence in America, and I will never stop fighting to get even more done."

The news came the day after the country was rocked by another school shooting, this one carried out by a 17-year-old armed with a shotgun and a handgun who killed a sixth grader and wounded five others on the new year's first day of classes at an Iowa high school, authorities said. The suspect, a student at the school in Perry, Iowa, died of what investigators believe is a self-inflicted gunshot wound.

It wasn't clear Friday how the shooter got the weapons, but people under 18 can't buy legally buy guns in purchases regulated by federal law.

The 2022 law was passed after a series of mass shootings, including the massacre of 19 students and two teachers at a Texas elementary school. The measure was a compromise that also included steps to keep firearms from more domestic violence offenders and help states put in place red flag laws that make it easier for authorities to take weapons from people found to be dangerous.

It mandates extra checks with state and local officials for young buyers, along with the FBI databases typically searched before someone is approved to buy a gun. Those steps have so far blocked 527 guns from being sold, Garland said.

Still, "This is not a time to relax our efforts," he said in remarks that also touched on overall declines in homicides in many U.S. cities. "We have so much more to do."