(Image credit: Arapahoe County Sheriff/AP Photo)

By CAROL McKINLEY and CHRISTINA NG

CENTENNIAL, Colo. - Accused Aurora shooter James Holmes legally bought thousands of bullets, explosives chemicals and four guns months before prosecutors say he opened fire on a crowded movie theater, an ATF agent testified today.

The agent testified on the second day of a preliminary hearing, which is essentially a mini-trial as prosecutors present witness testimony and evidence to outline their case against the former neuroscience student.

Agent Steve Beggs gave the prosecution a timeline that showed Holmes started his buying spree on May 10, 2012 with the online purchase of tear gas grenades. From then until July 14, Beggs testified, Holmes legally bought nearly 6,300 rounds of ammunition, two Glock .40 caliber pistols, a .223 caliber semi-automatic rifle, a 12-guage shotgun, ballistic protection clothing, beam laser lights, bomb-making material and handcuffs. Some of the purchases were made online and some were made in person.

Video surveillance taken as Holmes was buying several of the items in person showed that he had what Beggs described at "reddish-orange hair" at the time. Holmes hair was dyed the same striking color at the time of the shooting.

Holmes' defense attorney Tamara Brady asked Beggs if there is a legal process to keep from selling these items legally in Colorado to a "severely mentally ill person." Beggs answered that there is not.

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The hearing at the Arapahoe County District Court in Centennial, Colo., could last all week. Judge William Sylvester will decide whether the case will go to trial. Holmes' attorneys have not yet said whether they plan on using a insanity defense, in which case Holmes could possibly be deemed unfit to stand trial. Another possibility is that the hearing could set the stage for a plea deal.

If the case does not go to trial, this week's hearing could be the only opportunity for public testimony and release of information in a case where gag orders and sealed documents have kept much of the evidence and information away from the public.