The man who shot and killed NFL player Joe McKnight has been indicted for 2nd degree murder ... officials in Louisiana announced.

Ronald Gasser, 55, was arrested on December 5 and booked for manslaughter ... following a road rage incident that led to the death of the former USC star.

Now, after further investigation by the Jefferson Parish Sheriff's Office in collaboration with the D.A., a grand jury has hit Gasser with the more serious charge of 2nd degree murder.

As a result of the indictment, the judge raised Gasser's bond from $500K to $750k.