Meyers, whose parents cared for Weiler and his siblings, said his cousin had been out of touch for several years after leaving Illinois.
A pastor at a homeless shelter operated by a church in suburban Kansas City, Mo., said Weiler lived there for about six months within the past year.
Doug Perry said Weiler showed no violent tendencies and was active in the group's food pantry and various ministries, but he was clearly troubled. Among other things, he blamed himself for his parents' deaths, Perry said.
"I knew he was in a bad place," the minister said. He said he last saw Weiler about three months ago, when he left to take a roofing job in Houston.
"We really, really tried hard to love Greg and put up with his sort of sullen detachment," said Perry, pastor of The Church of Liberty in Liberty, Mo. "We poured a whole lot of love, a whole lot of time, a whole lot of prayer into trying to help him. I grieve because I really do love the kid."
Perry's church opposes denominational divisions and advocates for one Christian church in each community.
"We're supposed to be ONE Body and we're supposed to be about JESUS," its website says. "We're not supposed to split off and let theologies and philosophies of Man and personal grudges divide us into little pieces."
Perry said his beliefs are based on Christian teachings and his church does not advocate physical violence or the destruction of buildings. He said it would not support any plan Weiler had to harm churches.
"We've never advocated any kind of violence at all," he said. "This has nothing to do with physical violence."
Back in Oklahoma, youth pastor Chris Carlisle of First Baptist Church of Miami, said the community in the northeast corner of the state is usually very safe and Weiler's arrest hadn't caused great alarm.
"We haven't changed anything," Carlisle said. "We just pray for him that God would do a work in his life. We know that God has a different plan for his life."
Associated Press writer Don Babwin contributed to this story from Chicago.