A Brookline, N.H., firefighter found out that his 30-year-old daughter died in an automobile crash after he arrived at the scene during his shift Christmas Eve morning, according to Brookline authorities. Katie Hamilton, a Brookline resident, was pronounced dead at the scene. Police officials in the southern New Hampshire town declined to identify her father. Hamilton’s Ford Explorer was struck from behind as she waited to make a left turn from Route 13 south to Route 130 around 9 a.m. Tuesday, according to a police statement. The collision with the pickup truck behind her, driven by a man police identified as Greg Cullen, 31, of Milford, N.H., caused Hamilton’s Explorer to lurch into the northbound lane of Route 13, where she was struck by another pickup truck driven by James Ciprotti, 37, of Weare, N.H. Neither Ciprotti nor Cullen were injured, police said. Authorities did not say if either face charges, noting that the accident remains under investigation.