(CBS/AP) OAK CREEK, Wis. - The weapon used in Sunday's mass shooting at a Sikh temple in this Milwaukee suburb, in which six people were killed and three wounded before the gunman was killed by police, was purchased legally, authorities said.

At a press conference Monday Special Agent Bernard Zapor of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives said the weapon, a 9 mm semiautomatic handgun with multiple ammunition magazines, had been obtained legally by the suspect, Wade Michael Page.

Wade was killed outside the temple in a shootout with police officers after the rampage that left terrified congregants hiding in closets and others texting friends outside for help.

Page served in the U.S. Army for about six years. According to sources in the Army, Page enlisted in April 1992 and was given a less-than-honorable discharge in October 1998. He served at Fort Bliss, Texas, in the psychological operations unit in 1994, and was last stationed at Fort Bragg, N.C., attached to the psychological operations unit. The details of his discharge were not immediately clear.

Page was a white supremacist, according to the Southern Poverty Law Center.

Carlson said the FBI is looking into possible ties to white supremacist groups, and that Page "had contact with law enforcement in the past," but officials said, to their knowledge, there were no pending investigations involving Page prior to Sunday's shooting.

"There may be references to [Page] in various files - those are being analyzed right now," Carlson said. Page's military's records are also being analyzed.

Carlson said it is too early in the investigation to tell whether it would be classified at a hate crime or as a possible domestic terrorism case.