Five people have been killed and several others injured in two shooting incidents at Christian centres in Colorado in the western US.
Two people were killed in the missionary training centre
A gunman fled after killing two people at a training centre for missionaries in the state capital, Denver.
Hours later, a gunman shot dead one person at a church in Colorado Springs before being shot dead by a security guard. A second victim later died.
Police are trying to determine whether the two incidents were connected.
Officers from Denver and Colorado Springs were reportedly co-operating to see whether there was a match between the description of the Denver shooter and the gunman killed in the second shooting.
Don Wick, chief of police in the Denver suburb of Arvada where the first shooting happened, said a link was possible.
"Yes, there's a reason to believe that," he told reporters without elaborating.
The first shooting happened just after midnight, local time, at a dormitory in the Youth With a Mission centre, in Arvada.
Tiffany Johnson, 26, and Philip Crouse, 23, were killed and two men aged 22 and 23 were wounded, police said in a statement.
The later shooting in Colorado Springs - 65 miles (105km) from Denver - occurred near the New Life Church, an evangelical congregation.
The gunman killed one person and wounded four others, before being shot dead by "a courageous security staff member who probably saved many lives", police said.
One of the people caught in the attack later died of their injuries, officers said.
In both cases the shooter was described as wearing black clothing.
However witness descriptions quoted by the Associated Press news agency differed in each incident.
A handgun was used in the Denver shooting, while a rifle was used in Colorado Springs, AP quotes police as saying.
The Youth With a Mission organisation is reported to have a small office on the New Life Church site.
The New Life Church is one of the largest in Colorado, with a congregation of over 10,000.
It was founded by Ted Haggard, who triggered controversy last year when a former male prostitute alleged Haggard had regularly paid to have sex with him over a three-year period.