CEDAR RAPIDS — A 15-year-old suffered life-threatening injuries in a shooting at Jefferson High School this morning.Police said the shooting was reported at 7:56 a.m. The victim was found behind the auditorium outside the school.The school was placed on lockdown, but officials said they don’t believe anyone other than the victim was involved.“The school has been secured and students are being held in place until we can gather more information,” read a message sent to Jefferson students.