The threat followed a week of lock-downs and evacuations at schools around the country in the wake of the Virginia Tech shooting massacre.
Shortly before noon Thursday, police took a male suspect into custody who they believe is responsible for Internet posting, Kalamazoo County sheriff's Lt. Terry VanStreain said.
He said the first message appeared at 5:02 p.m. Wednesday and read: "My friends and I were sitting around yesterday discussing how we don't have any killers in our generation, then I heard about this (expletive). Thank you, God, for answering my prayers."
A second message, posted before dawn Thursday, read: "Our government kills that many people every day. ... The only reason you give a damn is because it's on CNN."
Another threat at the University of Minnesota had forced the evacuation of eight buildings on Wednesday, but they were open again Thursday after several hours of searching, university police Chief Greg Hestness said. He said officers found nothing unusual after investigating the bomb threat.
Classes also were canceled Thursday at Catholic High School near Ann Arbor after police found the words "Virginia Tech today" written on a bathroom wall. Washtenaw County Sheriff Daniel Minzey said police had identified the student or students responsible and would seek criminal charges.
In St. Augustine, Fla., a 14-year-old high school student was charged with a felony for threatening in an e-mail between friends to top the Virginia Tech massacre by killing 100 people, St. Johns County sheriff's spokesman Chuck Mulligan said Thursday. He said the boy had made similar threats before and was being held at a juvenile detention center.