Sketch of possible Virginia Tech gunman released

Daffodils bloom as students play Frisbee and head to classes on the Drill field at Virginia Tech in Blacksburg, Va., Tuesday, April 8, 2008. (AP Photo/Steve Helber)
AP Photo/Steve Helber
Composite sketch of possible gunman seen on the Virginia TechTech University campus, Thursday, August 4, 2011

(CBS/AP) BLACKSBURG, Va. - Police have released a composite sketch of a possible gunman reportedly seen on the campus of Virginia Tech University Thursday morning.

Three children attending a summer camp on the Blacksburg, Va. campus said they saw a man holding what looked like a gun.

The campus remains on lockdown and people have been ordered to stay indoors. There haqve been no other reported sightings.Policeklice

The university issued the first alert on its website at 9:37 a.m. Thursday.

The children said they saw a man walking fast toward the volleyball courts, carrying what might have been a handgun covered by some type of cloth. Police swarmed the area but said they could not find a gunman matching their description. The university said on its website that no one else has reported a person with a gun or anything suspicious.

An alert on the school's website said the gunman was reported near Dietrick Hall, a three-story dining facility steps away from the dorm where the first shootings took place during the April 2007 massacre at Virginia Tech that left 33 people dead, including a student gunman.

Officials said the person they were looking for Thursday was wearing a blue and white striped shirt, gray shorts and brown sandals. He was described as clean shaven, according to the university's website.