WACO, Texas - President Barack Obama, standing before a line of flag-draped coffins, consoled family and friends on Thursday at a memorial service for firefighters killed in a massive explosion last week at a Texas fertilizer plant.The deaths of 14 people, nearly all of them emergency responders, ripped a hole in the heart of the town of West, where farming is a way of life and where many people volunteer for the fire department in their spare time."To the families, the neighbors grappling with unbearable loss, we are here to say you are not alone. You are not forgotten. We may not all live here in Texas, but we're neighbors, too," Obama told more than 9,000 mourners who packed a basketball arena at Baylor University in Waco.The April 17 explosion at the West Fertilizer Co plant obliterated a residential section of West, about 20 miles (32 km) north of Waco.Investigators have not determined the cause of the blast, which also injured some 200 people.A video testimonial for each victim were read by a relative or friend and broadcast on a large screen behind the podium.In one video, Carmen Bridges, wife of Morris Wayne Bridges Jr., 40, fought back tears as she told of the last time she had seen her husband. As he rushed out the door to respond to the fire in West, he stopped to hug his 2-year-old son."'Daddy loves you and he'll be right back,'" Bridges recalled her husband telling the boy. "And he didn't come back."As the name of each victim was read aloud, a bell rang, echoing through the vast arena, where a dozen coffins - most covered with US flags, and a couple covered with Texas flags - were lined up in front of the stage.Obama and his wife, Michelle, both wiped tears from their eyes as bagpipers played "Amazing Grace" and the song filled the arena.The April 15 Boston Marathon bombings and the search for the suspects last week often overshadowed the Texas tragedy in the national news media.But Obama sought to assure Texans they were in his thoughts. He vowed that federal and state authorities would help to rebuild the town of 2,800 residents."Know this, for the eyes of the world may have been fixed on places far away, our hearts have also been here through times of tribulation," Obama said.