Police tonight arrested a 30-year-old man as part of their investigation into the Nov. 3 slayings of two men and the wounding of two others at a shipyard.

The man, who was not identified, was "a person of interest very early on in the investigation," police Capt. John Diaz said. The man was being questioned and held for investigation of homicide and attempted murder.

Diaz would not comment on a specific motive but said it was "a workplace violence issue. . . . He was tied in to the shipyard."

Diaz refused to discuss the man's links to the Northlake Shipyard, a boat repair business.

The man was questioned but not immediately booked into jail, said police spokeswoman Pam McCammon.

Marine engineer Russell James Brisendine, 43, and bookkeeper Peter Giles, 26, were killed in the attack by a man wearing a coat over camouflage. They were slain with a semiautomatic handgun.

Police have said the killings were deliberate but the motive remains a mystery. On Sunday, a handgun and camouflage jacket were found in a nearby park.

The gun and other items recovered in Gas Works Park near the shipyard "provided some assistance" in the investigation, McCammon said.

TV station KOMO reported that police served a search warrant this afternoon at the man's residence in the greater Seattle-Tacoma area.

Tim Walter, 24, of Lynnwood said he found the gun and other items Sunday and showed them to city police on Monday, KOMO reported. On Nov. 3, a man wearing a baseball cap, sunglasses and a dark overcoat over camouflage clothing strode into the shipyard office without a word and opened fire with a 9mm semiautomatic handgun.

One of the fatalities, Giles, was a nephew of the shipyard owners.

Walter, an electrician apprentice, said he was riding a bicycle with a friend at the park Sunday afternoon when he noticed a black, mildewed Nike backpack in some blackberry bushes, said KOMO. Wearing leather gloves, he pulled the bag through the thorny tangle, opened it and found a loaded handgun in one pocket of an Army surplus camouflage jacket, an ammunition clip in the other pocket, a pair of high-top sneakers, a toiletry bag, a gun holster and a folded leather cowboy hat.

Walter said the possibility of a connection with the shooting didn't occur to him, so he returned the bag to the bramble and kept the gun "as something I could sell or whatnot." Instead, his father persuaded him to report his discovery to police.