Bill Kennedy remembers the time, decades ago, when a roof collapsed on him while he was fighting a fire in Brooklyn.

Trapped for 30 minutes below the debris, his fellow firefighters struggling to dig him out, he feared he would "drown with all the water in the place."

That's another reason the past several days have been difficult for Kennedy, as well as the rest of his family, who has been waiting a week for word of what happened to his firefighter son, Tom. The younger Kennedy, 36, of Islip Terrace, was among those who reached the World Trade Center soon after it was hit by the first airliner.

Some members of Tom Kennedy's company in Divison 11, Battalion 32 survived the inferno and later spoke to his wife, Allison, 30. "They were all excited to go to the fire," Allison said. "That's what they live for. I don't imagine that anyone in his right mind could have imagined another plane going through another [tower] building."

The couple has two young sons, Michael, 2, and James, 9 months. His mother said that Michael "is carrying a toy telephone, saying [into the receiver], 'Where's Daddy? What happened to Daddy?'"

Yesterday, much of Tom Kennedy's family, including his parents and his two brothers, was gathered apprehensively at his home, hoping for a happy answer to that question. "Everybody is taking it really hard, [but] you can't give up hope," his father said. "We keep in contact with his firehouse. There's a possibility that he's still alive" in an air pocket under tons of rubble.

Bill Kennedy and his wife, Eileen, Tom's mother, were at their retirement home in Virginia on Tuesday morning and watched the attack on television. "I knew [Tom's] company was going to go there," his father said, since their Brooklyn firehouse is just across the East River from downtown Manhattan. "As soon as we heard [the news], we drove up," he said.