A San Antonio police sergeant and six other members of the force are under investigation after the sergeant crashed a patrol car into a highway wall early Thursday and the others tried to cover up the incident, Police Chief William McManus said at a news conference Monday. The 20-year veteran of the Police Department, off-duty and possibly driving while intoxicated, sideswiped a wall near East Josephine Street around 5:30 a.m., McManus said. The sergeant then walked…