Two weeks ago, his colleagues in the firehouse on Queens Boulevard in Woodside gave a party for Lieut. Thomas A. Williams to celebrate his 30th anniversary as a New York City firefighter. Yesterday, they were planning his funeral with his family.

Lieutenant Williams of Rescue Company 4 died of injuries he suffered when he fell or was blown from a large second-story window of a three-story mixed-use building in Maspeth, Queens, during a blaze late Monday night. Yesterday, marshals declared the fire arson, said Tom Kelly, a Fire Department spokesman.

Lieutenant Williams will be buried on Friday on what would have been his 53d birthday — the first city firefighter killed in the line of duty this year and the third in the last 12 months.

He left behind a wife, two college-age daughters and a reputation among his colleagues in Rescue Company 4 and Engine Company 292 as a firefighter who loved his job, spoke his mind no matter the consequences and defended his fellow firefighters.

Celebration and Sadness

Yesterday, in the firehouse at 64-18 Queens Boulevard near 65th Place, the American flag flew at half staff and purple and black bunting announced his death. Capt. Martin McTigue, who had been discussing by phone the details of the funeral with Lieutenant Williams's widow, Patricia, and two daughters, Kathleen, 21 years old, and Kristen, 19, recalled the bittersweet happiness of the party for his 30th anniversary, Feb. 10.

“A lot of old friends and old colleagues came by,” Captain McTigue said. “He was so happy to see all the men he had worked with. He was the man of the hour. He was sad, too. He was coming to the end of his career and he knew he was not going to be doing another 30 years. He knew retirement was coming closer and he wasn't looking forward to it.”

Firefighter Michael Milner, who was with Lieutenant Williams when the fatal plunge occurred, suffered leg injuries in the fall. He and nine other firefighters were treated for injuries at the City Hospital Center at Elmhurst and released. None of the half-dozen tenants rescued from the fire was injured in the blaze, which was first reported at 11:05 P.M.

Fire marshals determined yesterday that a flammable liquid was used to start the fire at the building at 66-45 Grand Avenue in Maspeth, but Deputy Commissioner Kelly did not say where the fire started.

The first floor of the gutted building consisted of a women's clothing store, Today's Styles, and a vacant store. On the second and third floors there were apartments in the rear; rooms toward the front appeared to have been used as storage space.

After responding to the blaze, Lieutenant Williams and Firefighter Milner went up an interior stairwell through intense smoke and were heading toward the rear apartments on the second floor when “a sudden expansion of superheated smoke and gases forced them to the front,” where they broke a large window to escape the heat and smoke, Deputy Commissioner Kelly said.

Firefighter Doug Sloan of Rescue 4, who was searching the first floor, recalled hearing Lieutenant Williams's call for help on a walkie-talkie: “I heard him give his mayday and I heard him yell to Mikey, 'Let's go, let's get out.' ”

Mr. Kelly said there was a “smoke explosion” and the two firefighters went out the window. “We don't know whether they fell or the force of the explosion knocked them out,” he said.

At an awards ceremony at Fire Department headquarters in Brooklyn yesterday, Mayor David N. Dinkins praised the dead firefighter, who had received seven citations for bravery in his career.

“Let us all pray that he is the last” to die in the line of duty, Mayor Dinkins said. “And let us offer up thanks that we are protected by heroes like Lieutenant Williams.”

A funeral is planned Friday at 10:30 A.M. at St. Joseph's Roman Catholic Church in Kings Park, L.I.