Phrase originally used by Philadelphia Phillies pitcher Brett Myers during a confrontation with a reporter which has now been used to alert others via text message about the death of a celebrity. This has developed into a competition to send your friend the "boom, outta here" message before he or she sends it to you.
However, this can also be used to signify the end of something
Nathan: Sending text message on 6/25/09
Michael Jackson - Boom, outta here
Jeff: Really? Shit!
Nathan: Did you hear that Brown won the election in Massachusetts?
Tim: Health Care Reform - Boom, outta here