GOLDEN, COLO. ? Authorities released nearly 1,000 pages of new documents from the Columbine High School massacre Thursday, including step-by-step plans written by the two killers as they gleefully plotted the deadliest school shooting in U.S. history.

“Hell on Earth – ahh, my favorite,” Dylan Klebold writes in the 1998 yearbook of Eric Harris above a drawing of a gun-wielding headless soldier. “So many people need to die.”

The documents released by the Jefferson County sheriff include essays, school work and computer files from Harris and Klebold, the two suicidal killers. The papers also included a journal kept by Harris’ father that refers to his son’s disciplinary and psychological problems but sheds no light on whether he knew the teen might be capable of the slaughter that left 13 people dead.

A scrawled entry in Klebold’s day planner apparently sketches out April 20, 1999, down to the minute, starting with a 6 a.m. meeting, a 10:30 a.m. “set up,” an 11:12 a.m. “gear up” and at 11:16 a.m., “HAHAHA.”

“Have fun!” Klebold writes in another notebook.

More than 20,000 documents and videos have been released since the attack, and some of the details released Thursday previously had been disclosed. Some documents include blacked-out portions, including song lyrics, names and computer logons. Sheriff Ted Mink also refused to release videotapes made by the gunmen, concerned they would encourage copycat attacks.

This document is among the nearly 1,000 pages the Jefferson County, Colo., sheriff's office released related to the 1999 Columbine High School massacre. The documents include essays, school work and computer files from Eric Harris and Dylan Klebold, the two suicidal killers.

But the new material offered chilling details about the killers’ activities in the months before the attack. They had “to do” lists, with each purchase of gasoline or a weapon marked off, and they had a hit list with at least 42 entries, all of them blacked out.

On a calendar entry for April 20, the time 11:10 is at the top – an approximate reference to the time the attack began. Elsewhere in the calendar are notations including “get nails” and “get propane, fill my clips” and “finish fuses.”

“Once I finally start my killing, keep this in mind, there are probably about 100 people max in the school alone who I don’t want to die, the rest MUST (expletive) DIE!” Harris writes in a journal entry from October 1998, six months before the attack.

The pages are filled with profanity, racial slurs and drawings depicting violence or death. Much of the Klebold material is handwritten, with detailed drawings of guns, sketches of what appears to be the Columbine cafeteria and his hopes for “500+” dead.

The Denver Post sued to force the release of the 936 pages. The Colorado Supreme Court left the decision up to the sheriff’s office, and the Harris and Klebold families did not challenge the decision.