Robert E. Coyle was born in Mahanoy City, Pennsylvania, on May 31, 1898. He attended St. Stephens' Grammar School in Philadelphia. In 1916 he enlisted in the United States Army, serving with the 108th Field Artillery during World War I. Prior to enlisting in the New Jersey State Police, Trooper Coyle worked as a chauffeur. He also served two years with the Pennsylvania State Police.

He enlisted in the New Jersey State Police on April 1, 1924 as a member of the 8th State Police Class, and was assigned to the Troop "B" substation in Pluckemin. His service with the New Jersey State Police was characterized by loyalty, fearless performance of duty and faithful and energetic devotion to the high principles of the New Jersey State Police.

Trooper Coyle's death was the result of gunshot wounds suffered while in the performance of duty.

On December 18, 1924, at about 5:00 P.M., Troopers John Gregovesir and Robert Coyle were escorting an attempted payroll robbery suspect to the Pluckemin Substation for questioning. The two troopers sat in the front seat, leaving the suspect unattended in the back seat. While driving along the highway near Chimney Rock, adjacent to Bound Brook in Somerset County, the suspect suddenly shouted "Hands Up!" Trooper Coyle, who was riding in the passenger seat, turned and the man fired a blank directly into Coyle's face. The man then wrested Coyle's revolver from him and fired two shots into Trooper Coyle's back. Trooper Coyle died immediately.

Trooper Coyle served 8 months with the New Jersey State Police.
He was survived by his wife of less than one year. He was 26 years old.