To come by chance; to come without previous expectation; to fall out.

come to pass; "What is happening?"; "The meeting took place off without an incidence"; "Nothing occurred that seemed important"

happen, occur, or be the case in the course of events or by chance; "It happens that today is my birthday"; "These things befell" (Santayana)

chance to be or do something, without intention or causation; "I happen to have just what you need!"