Two teens are dead following a car crash in Pere Marquette Township. The accident happened yesterday around noon on Pere Marquette Highway. 19-year-old Casey Jean O'Brien, of Branch, attempted a u-turn, near the ramp, and in the process was hit by a semi-truck. O'Brien died instantly. Her passenger, 18-year-old Nicholas Allen Smith, of Baldwin, was taken to Spectrum Health Ludington Hospital where he later passed away due to injuries sustained in the crash. His younger sister, 10-year-old MacKenzie Smith, was in the backseat, and is currently in critical condition at DeVos Children's Hospital in Grand Rapids. The two teens leave behind a 5-month-old daughter. Through investigation, it is believed the three were on their way to Michigan's Adventure and were attempting to find the southbound US-31 on-ramp, which they had passed, and were attempting a u-turn to return to it. The driver of the semi-truck, a 28-year-old Ludington man was uninjured in the crash.