The semi-automatic handgun used in the deadly attack on the Wisconsin Sikh temple is the same type used in other recent US mass shootings.
James Holmes, the man accused of killing 12 people in a shooting spree last month at a theatre in Aurora, Colorado, used one. 40-calibre Glock handgun and had another in his car
This includes one at a theatre in Colorado and the attack on a congresswoman in Arizona, gun experts said.
Wisconsin shooter Wade Michael Page used a Springfield 9mm semi-automatic to carry out the attack at a Sikh temple in Oak Creek, Wisconsin, officials said.
As in several other recent mass shootings, the gun had been purchased legally, at a Milwaukee-area gun store called the Shooter Shop.
Mr Page lived in North Carolina before moving to the Milwaukee area.
He was issued with five separate gun purchase permits in North Carolina after passing a background check in May 2008, according to the Cumberland County, North Carolina, sheriff’s office.
Semi-automatic handguns are the weapon of choice for mass murderers because they are light and easy to conceal, and adaptable to using high-capacity magazines, experts say.
This allows the shooter to fire the maximum number of bullets in a short period of time, said Josh Sugarmann, executive director of the Violence Policy Centre, a non-profit group that advocates to reduce gun violence.
Authorities said on Monday that Mr Page emptied several magazines in the shooting, and several more unused magazines were found.
A police officer who arrived on the scene early in the attack was shot at least eight times and survived in critical condition, Oak Creek Police Chief John Edwards said.
Other recent attacks have also used semi-automatic handguns with high-capacity magazines.
James Holmes, the man accused of killing 12 people in a shooting spree last month at a theatre in Aurora, Colorado, used one .40-calibre Glock handgun and had another one in his car.
The weapons were purchased legally within the previous 60 days.
Jared Loughner, who is accused of killing six people and critically wounding Representative Gabrielle Giffords in a January 2011 attack in Tucson, Arizona, used a Glock 9 mm semi-automatic pistol with a magazine that held more than 30 bullets.
He also had legally purchased the gun at a local shop and bought ammunition at Wal-Mart.
Seung-hui Cho, the Virginia Tech University student who killed 32 people and then committed suicide in 2007, also used a Glock semi-automatic handgun.