The sheriff's office in Jacksonville, Fla., says a "mass shooting" has taken place at a Madden video game tournament.

The Los Angeles Times reported the shooter was a gamer who was competing in the tournament and lost. Citing messages from another player in the room, the Times said the gunman appeared to target several victims before killing himself. Reuters could not immediately confirm that account of events.

The Jacksonville, Florida, sheriff's office is warning people to stay away from a riverfront entertainment district there known as the Landing, after a mass shooting event Sunday. Multiple fatalities at the scene, many transported. We can't stress enough to stay away. Local news sources report that 11 people were shot and four killed in the shooting, and the sheriff's office says that one suspect is reported dead at the scene. The shooting occurred at a Madden football video game tournament taking place at the Landing.