What is pro-mortalism, the belief held by Guy Bartkus?

Guy Bartkus, the man suspected of bombing outside a California fertility clinic, described himself as “pro-mortalist,” according to reports. - (FBI)

The man suspected of bombing outside a California fertility clinic expressed “nihilistic ideations,” authorities said on Sunday – and had written a “pro-mortalist” manifesto, according to unverified reports.

Guy Edward Bartkus, 25, was attempting to livestream the bombing attack on American Reproductive Centers fertility clinic in Palm Springs, authorities said during a Sunday press conference.