Problem after last security update
I installed security update on my macbook (Late 2009 with El Capitan). At the beginning of the reboot it made a loud sound and while it was starting, it restarted again, but it did not load anymore. it showed the screen with the logo and the progress bar all black. I forced the shutdown and then I started it again, but with the same result. How can I solve the problem?
VIN, MacBook (13-inch Late 2009), OS X El Capitan (10.11.6)