BAILEY, Colo. -- Investigators trying to piece together why Duane Morrison picked Platte Canyon High School to take six female students hostage before killing one and himself confirmed Monday that Morrison circled the school's parking lot a day before the attack.

Surveillance tapes from the campus show Morrison driving his Jeep at least once around the parking lot, said Lance Clem, a spokesman for the Colorado Bureau of Investigation. The sheriff had said previously that video showed Morrison at the school for about an half-hour before the attack began.

Park County Sheriff Fred Wegener said Morrison also asked some students their names, though he didn't specify if they were female students whom he knew or was trying to get to know.

"This still doesn't answer my big question, which is `Why?' We are still trying to find out whether this was a random act or whether this was targeted or if there was something about this school," Wegener said.

Investigators believed that Morrison had camped out near the school and have found two weapons, including an assault rifle, linked to the gunman.

Morrison's siblings issued a statement that did not offer any clues into his motive.

"The reported actions of Duane are inconsistent with all we know about Duane and how he lived his life," the family wrote in a statement released Monday. "Nothing about Duane or our relationships with him suggested that he would ever do something like this."

Emily Keyes, 16, died Wednesday after Morrison shot her in the back of the head before shooting himself as the Jefferson County SWAT team mounted a rescue mission.

Morrison, 53, lived in the Denver area for 10 years and recently drove and camped in several Western states, his family said in a statement.

"We would first offer our prayers and concerns for the family of Emily Keyes. We realize that they have suffered a loss that no family should have to bear," the statement read.

Morrison wrote a 14-page suicide letter that he mailed to a family member from the Shawnee Post Office a mile from the school the morning of the shootings in which he alleged abuse.

"Your father chose me to be the one. I've lately begun to wonder whey he chose me to be the one. Do any of you know?," he wrote according to media reports. "Why would a parent mentally and physically abuse a child? Not knowing where he was or when he would be coming after me, that was the worst."

Classes, canceled after the shooting, were to resume Thursday with a rescheduled home football game set for Tuesday afternoon at the school's athletic field.