ABC NEWS' PIERRE THOMAS, RICHARD ESPOSITO AND JACK DATE REPORT:
ABC News has learned that all four guns involved in the NIU shooting were purchased legally from the same Champaign, Ill., gun dealer. The Remington shotgun and the 9 mm Glock were purchased Saturday. The Hi Point 380 was purchased Dec. 30, 2007 and the 9 mm S Sauer was purchased Aug. 6, 2007 from the same gun dealer.
The suspect purchased each of the weapons himself.
The shooter had no arrests and no history of mental illness, according to law enforcement officials, which means he qualified under the state's law for gun ownership.
The gunman was armed with the 12-gauge shotgun, .22-caliber pistol and a 9 mm pistol. All were recovered at the scene.
At a location outside the scene a .45-caliber Glock semi-auto was also found. It has been linked to the gunman.
It's unclear where the fourth gun was purchased.
ABC has not yet confirmed that the gunman had a state-required Firearm Owner Identification or whether someone bought the guns for him.
The FOID background check is thorough, the Bureau of Alcohol, Tobacco, Firearms and Explosives says. Once the process was completed, a prospective buyer could have his weapon after a 72-hour waiting period for handguns and a 24-hour period for long guns.