Thomas X. Mackey, Police Lieutenant

Thomas X. Mackey, a retired Sag Harbor Village police lieutenant, died on Nov. 4 at home in Bonita Springs, Fla. He was 55. The cause of death was an apparent heart attack, his brother, Chip Mackey of East Islip, said.

As the executive officer of the department, which he served for 21 years, he was its second in command. He had previously worked as a Housing Authority police officer for the New York Police Department after finishing at the police academy. He still lived in his hometown of East Islip at the time, and when he received a letter inviting him to join the Sag Harbor force, he and his father got out a map of Long Island to figure out exactly where the village was, he once recalled. 

After his retirement in 2009, he taught criminal justice and co-wrote a book. He was an adjunct professor and graduate research adviser in the forensic studies department at Florida Gulf Coast University in Fort Myers while he continued his own studies, earning a master’s degree in criminal justice from the same university in April 2012. 

He was in the midst of completing a doctorate program at Capella University and was due to present his dissertation after Thanksgiving, his brother said. 

While he excelled at police work and got great joy from helping others, he came to find that he loved academia. “He was a brainiac,” his brother said. “Where he got his solace was going into the library and doing research.” He also enjoyed teaching, and in his students he found a receptive audience. 

He was the program director of criminal forensics at Keiser University in Florida for a year. He was also the director of the mass-killer database at Florida Gulf Coast University, the largest privately held database of its kind in the world. In his role there, he conducted research on sexual serial homicide. 

“Deviance: Theories on Behaviors That Defy Social Norms,” of which he and Duane L. Dobbert were editors, was published in July 2015. He was working on a second book.

Born Thomas Xavier Mackey on Sept. 25, 1961, at Glen Cove Community Hospital, he was known as T.X. to his friends and family since he was a child. He was the youngest of three children of Charles P. Mackey and the former Miriam A. Lynch. After attending East Islip High School in 1979 and taking college classes on Long Island, he graduated from the State University at Oneonta in 1983. 

An uncle who had served in the F.B.I. spurred his interest in pursuing a career in policing, his brother said. 

Once he joined the department in Sag Harbor in May 1988, he moved up the ranks, serving as a detective, then as a sergeant, and finally as lieutenant and executive officer. He was also involved in establishing a police dive team in Sag Harbor in the early 1990s, before the Sag Harbor Fire Department took over such rescue efforts.

Colleagues said he was dedicated to the community he served — he once helped organize a youth Olympics attended by 400 children — and that he strived to make a difference in people’s lives. They recalled his interrogation skills and keen ability to read people. 

A physical fitness enthusiast, Mr. Mackey was a runner and a swimmer. While living in Sag Harbor, he swam year round in the master’s program at the Y.M.C.A. East Hampton RECenter. 

He was credited with saving at least two lives in the water. Once while on duty he rescued a suicidal man who had jumped from the bridge between Sag Harbor and North Haven. While taking a jog in August 2009, he rushed into Noyac Bay and pulled an unresponsive man out of the water off Long Beach and resuscitated him.

Several times he was named the department’s officer of the year, honored at the Southampton Kiwanis Club’s annual dinner.

In addition to his brother, his two children, Liam Mackey, 24, and Sheila Mackey, 19, both of Sag Harbor, survive him. A marriage ended in divorce. He leaves two nieces and a nephew.

His parents died before him, as did a sister, Sheila Mackey, in an automobile accident in 1978. He had two cousins who were like brothers, Kyle Lynch of Springs, who survives, and Ryan Lynch, an East Hampton Town police sergeant who died in 2005. 

A wake will be held tomorrow at Frederick J. Chapey & Sons Funeral Home in East Islip from 2 to 4:30 and 7 to 9:30 p.m. A Mass will be said at St. Mary’s Catholic Church in East Islip on Saturday at 9:15 a.m. The Rev. Hugh Cannon will officiate. Mr. Mackey was cremated and will be buried at St. Charles Cemetery in Farmingdale, next to his parents and sister.