Authorities in St. Clair County are investigating a fatal accident that happened on Illinois Route 50 just before 9:30 pm. Fox 2 has learned that a domestic dispute in a semi-tractor trailer cab between a man and a woman caused the accident. The woman is said to have jumped out of the big rig along Route 50 at Scott Troy Road. That action caused 5 other vehicles to crash. The crash left 1 person dead and 4 others injured. The injured were transported to the hospital. It’s not know if the woman who jumped out of the semi was injured.