LITTLETON, COLO. ? Hours after Dylan Klebold and Eric Harris killed 13 people at Columbine High School, authorities obtained search warrants for their homes using year-old evidence.

Sheriff’s officials had said in 1998 there wasn’t enough evidence of a crime to pursue reports that Harris and Klebold were threatening others and making bombs.

After the two killed 12 students and a teacher before killing themselves on April 20, 1999, the 1998 reports were used to obtain search warrants, according to documents re-leased Friday under court order.

They show for the first time that a warning about Harris from Randy and Judy Brown had been used to get permission to search Harris’ home and Klebold’s. In March 1998, the Browns gave authorities violent writings from Harris’ Web site, including a death threat against their son, Brooks, and descriptions of pipe bombs.

Investigators drafted an affidavit to justify a search of Harris’ home but never showed it to a judge.

“The longer I think about it, the madder I get,” Judy Brown said of the documents, released after an open records request by The Denver Post.

Sheriff’s spokesman Jim Shires said the full value of the report may not have been clear in 1998. “Obviously, anything that’s going to be in hindsight is 20-20,” he said.