The FBI began a domestic terrorism investigation of the group in February, and a confidential source attended its meetings in southwestern Kansas.
In a June meeting, Stein brought up the Orlando nightclub shooting, and proposed carrying out a similar attack against Muslim refugees in Garden City, according to the complaint.
They ultimately decided to target the apartment complex because of the number of Somalis who lived there and the fact that one of the apartments was used as a mosque. The complex houses about 120 Somali residents, Beall said.
The complaint said that Stein discussed the explosives used in the 1995 bombing of the federal building in Oklahoma City by Timothy McVeigh.
The men, who were arrested in Liberal on Friday morning, performed surveillance of the apartment building and prepared a manifesto, Beall said.
In a profanity-laced conference call that law enforcement monitored, Stein said the only way "this country's ever going to get turned around is it will be a bloodbath," according to the complaint.