Two people, including the gunman, were killed in the in Sunday's shooting at a Church in Colorado Springs, Colo., police said.
Colorado Springs police chief Richard Myers told a news conference that four other people were hospitalized and some of them have life-threatening injuries.
The gunman, who hasn't been identified, was shot dead by a church security officer, Myers said.
He said several suspicious devices were also located, and police and fire crews have been doing a methodical building by building search.
Meyers said the police received a 911 call at about 1:10 p.m. (2010 GMT) about the shooting in the New Life Church and arrived at the scene within minutes.
Law enforcement officials confirm that simple pyrotechnic devices were found in a suspect vehicle.
"It's a sad day and a tragic day in Colorado Springs," said Colorado Springs Mayor Lionel Rivera.
"They came to church to worship, what happened today was a tragedy," said pastor of the New Life Church, Brady Boyd.
"It's unfortunate that we live in a society where this happens, but it does," he told reporters.
This is the second such shooting in Colorado in the same day.
Police in the Denver suburb of Arvada said two people were killed and two others were wounded when a lone gunman opened fire at a training center for Christian missionaries early in the morning. The gunman is still at large.
The shooting occurred at about 12:30 a.m. (730 GMT) at the Youth With a Mission center.
About 50 people were in the center when the gunman opened fire.
Colo. Governor Bill Ritter issued a statement in response to the two shootings.
"Today, Colorado mourns the tragic loss of those killed and injured in two senseless shootings. Our deepest sympathies go out to the families of those who were taken from us, and we pray for the speedy recovery of those who were wounded," he said.
The governor said he have activated the Colorado Information Analysis Center, and have directed the Department of Public Safety, Colorado State Patrol and the Colorado Bureau of Investigation to provide immediate assistance to the local and federal agencies investigating the shootings.