Four years ago, Lowell firefighter Kelly Page was given the state's highest award for bravery after he entered a burning apartment to rescue two people. After the ceremony, photographers snapped photos of Page cradling his 18-month-old daughter in his arms as she gnawed on his silver medal. Yesterday, Page's young family was mourning his death late Friday night, apparently from a heart attack, several hours after he had responded to a routine call to a basement fire at a vacant building. Another firefighter found Page, 38, about 8:15 p.m. collapsed on the floor in the garage of the station on West Sixth Street, several feet away from the fire truck and medical equipment he had just been checking. Fire officials said his heart attack was either too massive, or he was discovered too late. "We'll never know," said Lieutenant Sean Ready, who tried to revive Page. "We did the best we could, we did the best we could. It's very difficult." Page, who joined the department after nearly a dozen years in the Navy, leaves a wife, Katie, and three daughters, ages 5, 10, and 13. He is the 23d Lowell firefighter to die in the line of duty, and the first since 1986, when John Barry Gannon died of almost identical circumstances. Barry was found by his colleagues after fighting a fire, suffering a heart attack. Members of the tight-knit, 200-member Lowell Fire Department were shocked yesterday by the death of Page, who went to the gym daily, watched his diet, and was a workhorse who was called on to do the most arduous jobs. "He was the guy at a fire, who if we needed a ceiling pulled or a door opened that was extremely difficult, you assigned it to Kelly and he'd get it done," said Deputy Fire Chief Patrick McCabe. "He was just a picture of health, probably 6 feet 2, 240 pounds, going to the gym every day. It's pretty shocking for all of us to see a guy like that die so suddenly," said Blake Galvin, a former linebacker at Boston College who several years ago recruited Page to help him run a free football program for teenagers who were too heavy or couldn't afford to play in other leagues. "This is truly a tragedy for the city of Lowell." Page grew up in Dalton, Ga. and still spoke with a Southern drawl that earned him a firehouse nickname, "The Rebel," that belied his happy-go-lucky attitude. "You could tell he wasn't born in these parts," McCabe said. "But his wife was from Lowell. Love brought him here." Over the years, Page had coached softball teams his daughters played on and had recently taken vacation time so his family could go to Ohio for one of his daughter's softball tournament. His wife is an elementary school teacher. The family declined interview requests yesterday. "He loved his family, he loved his friends, and he loved his career," the family said in a statement. Firefighters called Page "the mayor of Belvidere," a nickname that referred to a residential section of Lowell and underscored his reputation in the community. He worked part time at the Powerhouse Health and Fitness Center and put in shifts as an emergency medical technician for Trinity Ambulance. "Everyone knew Kelly Page," said Eric Broadhurst, who owns the fitness center and hired Page to work the desk and recruit members. "I told someone today, if you stopped 20 people on the street and none of them knew Kelly, I'll give you $1,000. This is a great loss to the city." City and fire officials are making preparations for a funeral later this week with full Fire Department honors "The last time I laid eyes on Kelly, we had an attempt to burn an old tenement on West Third Street, and he was in the building, trying to find the source," said McCabe, recounting the scene that Page responded to shortly before his death. "He was carrying an ax, and he was all set to go to work. He was all set to go. That's what I keep seeing in my mind." Several hours later, Ready discovered Page on the floor, near the fire truck. Page was taken to Saints Medical Center in Lowell, where he was pronounced dead. "He was a great firefighter, a great guy, and a tremendous asset to the department," said Fire Chief Edward J. Pitta. "As you can imagine we're all reeling from this." We all will miss Kelly! A True Hero!