I would guess the number one way he was found was internal security systems in each of the hacked systems.
Cybersecurity involves lots of automated systems that "alert" system admins when it comes to strange patterns.
Like... This user is logging in from an unrecognized IP from an unrecognized geo-location during a time the user usually would be asleep. The user in question has never logged into the system from that area or IP, nor do they do it when they're off the clock in the middle of the night. These unusual details would trigger an alert sent to a sysadmins cell phone, and from them they would begin digital forensics to try to pick up the trail of who this was.
Not excusing his actions but, as an Australian, I find child support a predatory system, the fact it basically cyphons people's finances, hurts their potential for growth and rehab, and the fact that I've heard so many stories of the parent never using the funds on their kids, but on their own greed and self fulfilment, which is just horrific, although I don't believe I know enough about this topic to have a truly well thought out opinion.
"Identity theft" is bullshit. They didn't steal an identity, they stole credentials. But even though those credentials were created and maintained outside of our consent, control, and often contrary to our interests, somehow we're responsible when they get stolen.
He then "assigned himself as the medical certifier for the case and certified his death, using the digital signature of the doctor," the press release said.
I get what you're saying, but I'm pretty sure credentials for medical certification are pretty damn important and not contrary to anyone's interest. It's literally to ensure a professional, who has the correct Authentication, Authorization, and Accounting, is actually altering State databases about citizens' deaths, and not just some rando like this asshole.
I would say a digital signature constitutes a type of forgery, and thus would fall under actual identity theft.
Great, did you notice that the system for Dr's authorization didn't leave it up to the Doctors to protect, monitor, and repair the damage caused when the credential was stolen? Did the Doctor's entire financial life get upended until the doctor personally corrected the error with all the appropriate government bureaucracy?
Identity isn't a digital token living in a database. The whole business implies that you're not a human being without a Social Security number, and who you are is issued by the credit reporting agencies and the government. My god man, do you really think your identity belongs to a company or the government?