Tensions ran high at Mount Vernon High School Friday after word of a threat spread across the grounds.

School officials say a student told the principal someone threatened to open fire with a gun on school grounds. Officials say word spread throughout the school with the help of cell phone text messaging. Students with parental consent were permitted to leave early.

Violence has been an issue at the school this week. On Thursday, two 17-year-old students were shot, one fatally, in broad daylight along South 7th Avenue. Earlier in the week, a police officer was assaulted by a student at the school.

Mount Vernon Police Commissioner David Chong says rumors of violence are rampant, creating ?self-generated hysteria.?