He graduated from Xavier High School in Manhattan in 1986, and earned a Bachelor of Science degree in business economics from the State University of New York at Oneonta.

[6] Shea started his career in law enforcement with his appointment to the New York City Police Academy in late 1990.

After graduating in the top 10% of his academy class, he was sworn in as a Police Officer in April 1991 and assigned to the South Bronx.

[5] As Commissioner of the NYPD, Shea stated in public testimony on June 22, 2020 that NYPD officers who had driven into protesters did not use excessive force and said that the officers who were in the vehicle were being "set upon and attacked, and thankfully they were able to get out of that situation with, to my knowledge, no injuries to anyone."

He also said in the public testimony that "Our internal affairs bureau investigated this information and preliminarily we have an accounting of that incident where we have officers in a situation where they're essentially being penned in by protesters.