WILMINGTON, Del. — A judge has handed down a 30-year sentence to a man who fatally stabbed a good Samaritan who came to the aid of a woman and her infant being chased by a knife-wielding assailant.

Twenty-seven-year-old Calvin Hooker III was sentenced Friday after a jury in April found him guilty but mentally ill of second-degree murder.

Authorities say Hooker will spend the next 30 years either in prison or a psychiatric center.

Hooker repeatedly stabbed 27-year-old Thomas Cottingham in September 2015 in Rodney Square, a central downtown plaza in Wilmington. Authorities say Cottingham intervened when Hooker, holding a knife over his head, chased a woman pushing her six-month-old infant in a stroller.

In addition to murder, Hooker was convicted of aggravated menacing, child endangerment, resisting arrest and weapons offenses.