The 26-year old attacker, who was a former-employee of the facility, has turned himself in to police and admitted to committing the attack.
This incident is the worst crime in Japan's postwar history.
facility - a place that provides a service to people
disabled (adjective) - having a mental or physical challenge / problem
to turn oneself in - to go to the police so they can arrest you after committing a crime
to admit - to confess doing something / being something
to commit __ - to do something (serious)
postwar - after the war (World War II)