LOUISVILLE, Ky. (AP) _ A printing plant worker apparently started buying up the high-powered arsenal he used to kill seven co-workers at the same time he quit his job because of mental illness, authorities said.

Police said Joseph T. Wesbecker was armed with several semiautomatic weapons and hundreds of rounds of ammunition Thursday morning as he went from floor to floor at the Standard Gravure Corp.

Wesbecker, 47, killed seven people and injured 13 before killing himself. Three of the injured were in critical condition Friday night.

The first funeral for a victim of the massacre was to be held today in Louisville. The victim, James F. Wible Sr., will be buried Monday in Forreston, Ill.

Police searched Wesbecker's home Thursday night and found the Feb. 6 issue of Time magazine open to a detailed article on similar shootings across the United States in the past two years, said Lt. Jeff Moody, police homicide commander.

Before he quit working, Wesbecker apparently owned only less powerful weapons. But on Aug. 26, 1988 - less than three weeks after he quit - Wesbecker purchased a semiautomatic 9mm pistol from Archery World & Guns in Louisville. Police said he used that gun to kill himself.

Two MAC-11 semiautomatic machine pistols were purchased last Feb. 10 - four days after the Time article came out - at Tilford's Gun Sales in Louisville. He bought an AK-47 assault rifle on May 1.

Meanwhile, state Rep. Mike Ward, D-Louisville, said he would sponsor a bill in the General Assembly to ban assault weapons in Kentucky.

''We owe it to the families and the other victims to try at least to make it harder for a deranged person to obtain the weapon,'' Ward said.

Nearly 90 percent of Standard Gravure's 360 employees met with grief counselors when they returned to the plant Friday morning. Several hundred later attended a Mass at the Roman Catholic Cathedral of the Assumption.

The plant's offices had been cleaned up overnight. Bullet holes in walls and ceilings were the only physical reminders of the tragedy.

Wesbecker was a pressman at the plant from 1971 until he quit on Aug. 8, 1988. The company placed him on long-term disability last Feb. 2 because of his mental problems - meaning he could never work at the plant again.

Relatives told police that Wesbecker was a manic depressive who had attempted suicide three times.

Wesbecker paid $349 for the AK-47 without revealing his mental problems on a federal form required for such purchases, said Jack Tilford, owner of Tilford's, and federal officials. About two weeks after he picked it up, Wesbecker returned and bought about a case of ammunition - 1,100 rounds - for $139, Tilford said.

Tilford said Wesbecker answered all eight questions properly on a federal Bureau of Alcohol, Tobacco and Firearms gun purchase form.

Moody said Wesbecker had spent time - voluntarily - in mental institutions, including Our Lady of Peace in Louisville. Police would not reveal when he had been hospitalized.