(CNN) -- Police in Arvada, Colorado, searched for a killer on Sunday, while a school for missionaries mourned the deaths of two of the gunman's victims and prayed for two others whom he wounded.
Investigators were looking for any connections between the shootings and a later assault on a church in Colorado Springs, but police officials would not discuss possible links Sunday afternoon.
In the Colorado Springs incident, a gunman attacked worshippers, killing one person and wounding four others before being killed by a security staff member, police said.
"We are not in a place to confirm any information about any possible similarities to these incidents, being widely reported throughout the media," Arvada Police Chief Don Wick told reporters. "I'm asking that all of our communities be vigilant until we determine who's responsible for these crimes."
Authorities described the Arvada gunman as a white male, roughly 20 years of age, wearing a dark jacket. He may have a beard or mustache and may be wearing glasses and a dark skull cap or beanie, police said.
Police confirmed that two of the four people shot early Sunday at the live-in training center for young Christian missionaries were dead, and identified them as Tiffany Johnson and Philip Crouse.
At about 12:30 a.m. Sunday, the gunman entered a building where Youth With a Mission members were cleaning up from a Christmas banquet, said Peter Warren, the center's co-founder.
He asked for housing for the night, Warren said, which Johnson refused to give him.
"She said, 'We really can't do that right now,' " Warren said.
"And then he opened fire."
Police had tried to track the gunman through fresh snow with the help of dogs, but lost his trail in a heavily walked area, deputy police chief Gary Creager told CNN. Watch police swarm around missionary center »
Johnson, 26, was from Minnesota and Crouse, 24, was from Alaska, police said in a statement. Warren said both Johnson and Crouse died in surgery.
The two other shooting victims are men, ages 22 and 23, police said. One was in critical condition with a bullet wound in his neck and the other was in stable condition with wounds on his legs.
Paul Filidis of Youth With a Mission's Colorado Springs office identified the wounded men as Charlie Blanch and Dan Griebenow, CNN affiliate KUSA reported. Both are staff members, according to the organization's Web site.
Johnson has been affiliated with the organization since 2006, and joined the staff in spring 2007, the Web site says.
Warren said a memorial service for the two dead would likely be held Tuesday or Wednesday. "These kids were like our kids, you know?" he told KUSA. "It's just such a tragedy."
Warren said the center was bringing the 80 or so other people who live at the Arvada campus to the group's mountain campus in Golden, Colorado.
"We're just going to be honest, and pray for one another, and cry with one another," he said.
Youth With a Mission was founded in 1960, and now operates in more than 1,000 locations in 149 countries, according to its Web site. The organization has a staff of nearly 16,000.
The center is home to dozens of young people from all over the world who are being trained as Christian missionaries, according to the center's Web site.
Arvada is a Denver, Colorado, suburb with a population of about 105,000. E-mail to a friend
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