Condition improves for sister of triplet, 11, killed in New Jersey school bus crash Matt Rourke / AP An Investigator views the scene of a school bus crash Thursday, Feb. 16, 2012, in Chesterfield, N.J. By The Associated Press and msnbc.com staff CHESTERFIELD, N.J. -- Hospital officials in New Jersey say the condition of one of the sisters of an 11-year-old triplet killed in a school bus crash has improved. A spokeswoman for Cooper University Hospital in Camden says Natalie Tezsla's condition has been upgraded to stable, from critical. But her sister Sophie Tezsla remains in critical condition, as does a third student. The girls are the daughters of a New Jersey state trooper. The crash Thursday in the town of Chesterfield, south of Trenton, killed the Tezslas' other sister - Isabelle. The accident occurred when a dump truck collided with the bus, which was carrying 25 children to an elementary school. An investigation into the cause continues and no charges have been filed. Police have identified the bus driver as John Tieman, 66, of Beverly. The driver of the dump truck was Michael Caporale, 38, of New Egypt. Read more on NBCPhiladelphia.com On Thursday, more than 200 mourners packed into pews at the Chesterfield Baptist Church, with more people outside, for a silent vigil, according to nj.com. It's a small town. They were sisters. It's sad, and we all hurt together," Karen Wainwright, a friend and neighbor of the Tezsla family, told the website. Chesterfield Baptist Church Pastor Edward DeSilva told NBCPhiladelphia.com: "It's sobering, it's devastating. You think of your own kids.  Students on the bus said they were wearing their seat belts, according to The Associated Press. Lori Morrow, a mom of one of the children on the bus, talked to NBC10's Lu Ann Cahn Thursday as she was on her way back to the hospital to be with her daughter. "She saw the dump truck coming at the bus and it didn't look like it was going to stop and she saw it smash right into the bus," Morrow told the NBC affiliate. It was a couple of seats above her where it smashed into the bus. It was horrendous. Despite seat belts, the children were thrown about the bus, Morrow told the TV station. All the kids got thrown into the aisles. They had their seat belts on apparently, but they didn't hold. "The family's grief must be enormous," New Jersey's governor, Chris Christie, said in a statement Thursday night. We can only imagine their pain, and lend our support and prayers in this most difficult of times. We are sure that all of Chesterfield Township, the family of State Police men and women, and indeed residents all across New Jersey, have the Tezslas in their thoughts and prayers. Our same concerns and prayers extend to the other children aboard the bus, particularly Jonathan Zdybel, the young boy who also remains hospitalized and in critical condition.