These incidents go back farther than Brandon Lee, in 1984 Jon Erik Huxum shot himself in the head with a prop gun a .44 magnum loaded with blanks. He was joking around and put the gun to his head and pulled the trigger. Blanks still have a danger factor to them.
https://ew.com/article/1994/10/14/jo...ms-fatal-joke/
I believe real firearms are still used on sets with blank ammunition. I also think before too much speculation goes on we wait for the investigation to be completed by the police. There is no doubt that given the high profile nature that details will be released.