HUDSON, Ohio (AP) -- A threatening note found in a golf course parking lot has led an Ohio school district to tighten security and notify parents.

Hudson schools Superintendent Steve Farnsworth told parents in an automated phone call Tuesday morning that the message found under a car's tire did not mention any particular school as a target. But it called Tuesday "the day it ends" and said, "Hudson will know."

There was also the sentence, "School is dangerous," and the words "bloody," "boom" and "bye."

Classes were held as usual in Hudson, 20 miles southeast of Cleveland. Spokeswoman Sheryl Sheatzley said the district was being cautious.