A church member and a gunman are dead and four people wounded after the gunman opened fire in a car park following a Sunday worship service at New Life Church, Colorado Springs police said.
Police were searching the sprawling campus of the 10,000-member church for reported bombs that may have been part of the shooting.
Officers said the gunman opened fire 30 minutes after a service ended and as many as 7000 people took shelter in buildings or fled as the congregation locked down.
Of the four wounded, three were admitted to Penrose Hospital, where one was listed in critical condition, one in fair condition and a third in good condition.
The status of the fourth victim was not available.
Pastor Brady Boyd said one of the dead was a New Life member.
“My heart is broken,” he said.
Hundreds of New Life members remained locked in church buildings for up to four hours as police searched for more gunmen, police Lt Fletcher Howard said.
Police asked the families of victims and witnesses to gather at the Rampart Range Campus of Pikes Peak Community College near Interstate 25 and Interquest Parkway.
Police said officers arrived at New Life two minutes after getting the first 911 calls of gunshots.
Mr Boyd said he heard the gunfire and was told by a church worker that there was shooting in the church.
“It was surreal,” he said.
Mr Howard said officers arrived to find a bullet-riddled car in the parking lot and several people with gunshot wounds.
It was unclear whether the violence at New Life was tied to an early-morning shooting at a training centre dormitory for young Christian missionaries in Arvada, a Denver suburb, that left two dead and two wounded.
“That is an open question,” Mr Howard said.
In that case, a lone gunman reportedly opened fire after he was denied shelter in the dormitory.
The gunman in that case fled and has not been found.
Mr Boyd asked for community support and said “please pray for those who were injured”.
The New Life shooting led to a huge call-out of local police, with dozens of police cars from more than three jurisdictions rushing to the church.
Colorado Springs Police Chief Richard Myers said federal agents from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives were also helping with the case.
ATF agents are the federal government’s bomb experts, who could help police identify and defuse what officers suspect are bombs still at the church.
“There are several suspicious devices identified,” Mr Myers said.
Churchgoers were herded into a basement of New Life by church leaders, who Associate Pastor Rob Brendle said were implementing a preset plan for violence at the church.
New Life members began gathering in the parking lot outside the church soon after the shooting.
One woman who asked to be identified only by her first name, Autumn, said she and other members felt a need to be near the scene of the violence.
“Just to be here and pray for our church,” she explained.
New Life Church made headlines last year when its nationally known pastor, Ted Haggard, stepped down after admitting to a long-term relationship with a male prostitute.
Sunday’s guest speaker at New Life was Jack Hayford, pastor of Church on the Way in Van Nuys, California, and one of the New Life spiritual overseers who helped them navigate through the Haggard problems.
Churchgoers on Sunday said they thought their troubles were over when they got a new pastor and seemingly left the scandal behind.
“Why would somebody walk into a church and do something like that?” asked New Life member Kim Ho-Fing-Loy, 16. “Especially with what just happened with Pastor Ted, this church just doesn’t need this any more.”