Denver ? In between his two deadly shooting sprees, church gunman Matthew Murray apparently posted a furious threat on the Internet to kill Christians. But whether the warning reached police before he struck again was unclear Tuesday.

The warning – and other anguished, despair-filled messages over the past few months – were posted by someone using the screen name “nghtmrchld26.” The postings paint a picture of a home-schooled Colorado youth once affiliated with the Youth With a Mission program – as 24-year-old Murray had been.

“I’m coming for EVERYONE soon and I WILL be armed to the (expletive) teeth and I WILL shoot to kill,” Sunday’s posting by nghtmrchld26 said.

“God, I can’t wait till I can kill you people. Feel no remorse, no sense of shame, I don’t care if I live or die in the shoot-out. All I want to do is kill and injure as many of you … as I can especially Christians who are to blame for most of the problems in the world.”

At least one visitor to the site was alarmed and contacted the FBI promptly, before the second attack, the site’s administrator said. But the FBI would not immediately confirm that.

The threatening message was posted on a site for former Pentecostals at 9:55 a.m. or 10:55 a.m. – the time zone was not clear, said Joe Istre, site administrator and president of the Association of Former Pentecostals.

Either way, that was several hours after Murray killed two people at Youth With a Mission, a training center for missionaries in the Denver suburb of Arvada, and at least two hours before he killed two more people at the New Life Church in Colorado Springs around 1 p.m.

Denver FBI spokeswoman Rene Vonder Haar said the agency began an investigation immediately after receiving a phone call at 10:30 a.m. on Sunday. She refused to discuss the nature of the call but said the information was passed on to police in Arvada and Colorado Springs.

However, Colorado Springs police Sgt. Scott Schwall said that police there did not learn the Murray family home’s address in Englewood until after the church shootings, and that a search did not begin until well after dark.

Arvada police spokeswoman Susan Medina confirmed that the FBI passed on information regarding the mission center shootings at about 10:30 a.m. She would not discuss the information in detail but said “we began work on that tip immediately.”

Medina said Arvada detectives did not go to Murray’s home and speak to his family until 3 p.m., well after the second attack. Medina said police cannot say with certainty who nghtmrchld26 is.

Murray was dismissed from Youth With a Mission in 2002 for what the training center has described only as health reasons. Youth With a Mission maintains an office at the New Life Church.

An autopsy determined that Murray killed himself with a bullet to the head after he was brought down by gunfire from a volunteer security guard at the church, authorities said.

The online threats appear to include whole passages lifted from a manifesto written by Eric Harris, one of the teens who carried out the 1999 massacre at Columbine High School – 13 miles from Murray’s hometown.