OKLAHOMA CITY (AP) _ The mournful skirl of a bagpipe pierced the air and agriculture workers planted a whitebud tree in a memorial garden Friday in a pair of ceremonies honoring victims of the Oklahoma bombing one month ago.

A bass-voiced, uniformed state trooper sang a hymn and a bagpiper played ``Amazing Grace'' at an annual service to honor all law enforcement officers killed during the year. The ceremony focused on the 12 federal officers who died April 19 at the Alfred P. Murrah Federal Building.

Joe Gallo, the Secret Service agent in charge in Oklahoma City, noted that the past weeks were filled with funerals and with waiting for the missing to be recovered.

``In some respects, it seems like more than a month,'' he said. ``In other respects, it seems much shorter than that.''

The body of the last of Gallo's five slain co-workers was brought from the rubble two weeks after the blast.

At the ceremony, Gov. Frank Keating promised state as well as federal prosecution of those responsible: ``Oklahomans have been grievously wronged. Oklahoma will see its day of justice.''

At a memorial at the state Department of Agriculture, Keating joined agriculture workers who planted a whitebud tree in memory of seven U.S. Agriculture Department employees killed in the deadliest domestic act of terrorism in U.S. history.

The tree was placed in the center of the Heartland Grove Memorial Park, a heart-shaped garden being erected in memory of bombing victims. The garden includes small redbuds along the perimeter to represent the 19 children killed.

``They're all beautiful,'' said David Higginbottom, whose wife, Adele, was among the seven USDA workers killed.

Later in the day, Keating and his wife, Cathy, planned to plant nine redbud trees on the grounds of the governor's mansion, three with white blossoms for the youngest victims, three red in honor of the rescue workers and three pink in memory of all the other victims.

Attorney General Janet Reno planned to pay sympathy visits Friday to families of victims and thank officers and prosecutors working on the case.

Timothy McVeigh and Terry Nichols have been charged in the attack, which killed 167 people and wounded hundreds more.