Officer John "Sully" Sullivan was a NYPD police officer who worked at the 55th Precinct. He was portrayed by Skip Sudduth for all 6 seasons.
John Sullivan was born in New York in 1957. He has a sister, Fran, who later moved to Orlando, Florida with her now ex-husband Mike. Sully joined the NYPD, starting work at the 55th precinct where his training officer was Tyrone Davis, Sr. The two men eventually became partners and were like brothers. Ty Sr however was in with a group of corrupt cops, including Cathal Finney, who discovered that Ty Sr was planning on turning the others in. He arranged for Ty Sr to be murdered in order to silence him. This hit Sully a lot, he stopped going to church after this day and described as "the worst day of his life". Sully later found out the truth about the murder but said nothing in order to protect the Davis family and to make sure Maggie Davis still got her late husband's pension.
Sully went through a few other partners, including one who would later accuse him of falsifying evidence, and another who committed suicide after being forced to retire. In 1999 he acquired a new partner in Tyrone Davis, Jr, the son of his first partner. Although initially reluctant to take Ty Jr on, the two men soon bonded and became firm friends. A year later, Sully met his new neighbour, Tatiana, who was Ukrainian. They fell in love and started dating, but Sully was shocked by the sudden appearance of her son Sergei, whom she had not mentioned beforehand. Sully did not know that Tatiana was really called Natasha and worked for a Russian mob boss, Fyodor Chevchenko.
The two were set to marry on September 11, 2001 in Atlantic City but the day's events caused the wedding to be postponed. They eventually married, with Ty as best man, in New York on October 1. A few months after their marriage, Sergei was beaten up by Chevchenko's men. Sully, with Ty, went to see Chevchenko causing Ty to get shot. Sully felt guilty at this, and Tatiana was not happy with Sully for interfering. She later left Sully, returning two months later claiming to have been with relatives upstate. In reality, she had been working at Chevchenko's club. When Sergei returned to New York later, he was murdered at Grand Central Station, as was Tatiana when she went to see Chevchenko. In retaliation, Sully murdered Chevchenko.
The loss of his family caused Sully to drink, and eventually he became an alcoholic. Ty, worried about his partner, and reported him to the union. Sully later begged Ty for help - a few days later, Ty, Bosco and Doc took Sully up to a cabin to dry out. Sully said some hurtful things to each of them, but with help was able to overcome his drinking problem and return to work.
The truth about Ty Sr's death came out in 2004 after Cathal Finney's son Brendan joined the force. Ty was partnered with Brendan and Sully with Sasha Monroe, who became pregnant with Ty's baby. Sully urged her to tell him about it, but she miscarried.
In the final episode, Sully decided to retire, since he had always worked at the 55 and did not want to work at another precinct. He now owns a cabin by a lake, where he spends his time fishing.
Irene Sullivan (mother)
Tatiana (wife) [deceased]
Sergei (stepson) [deceased]
Tatiana (wife) [deceased]