37-year-old Marc Lamparello faces charges not just in the St. Patrick's incident, but also in New Jersey, where two days earlier he refused to leave a Newark church. Before heading to St. Patrick's, Lamparello reportedly purchased a $2,800 plane ticket to Italy that was set to leave the day after he was apprehended outside St. Patrick's. In December, Lamparello had gone to New Jersey police with claims that he was being stalked by a police vehicle outside his home.

In July 2019, Lamparello was declared mentally unable to stand trial. Both his family and his lawyer detailed his erratic behavior in the months prior to his arrest, and Lamparello admitted to police that he had stopped taking his medications prescribed for schizophrenia and bi-polar disorder.

Lamparello was to be admitted to a mental health facility but was released on March 20, 2020 before being assigned treatment as part of precautions the city was taking to decrease overcrowding at jail facilities during the coronavirus outbreak. Just days later, he attempted to injure himself and was taken to Bergen New Bridge Medical Center in Paramus, NJ, and shortly after his release, he died by suicide on the one-year anniversary of his attempted arson at St. Patrick's Cathedral.

The attempted arson in 2019 came just days after both a devastating accidental fire at Notre-Dame Cathedral in Paris and a string of arsons of historic churches in Louisiana that resulted in hate crime charges against a 21-year-old.