The death of a suspect in an armed robbery in Old Saybrook Monday was caused by gunshot wounds following a shooting with state police in Westbrook, state police announced Wednesday.

Twenty-four-old Jonathan Alvarado, whose last known address was in Deep River, died of gunshot wounds, according to the state Office of the Chief Medical Examiner. A second suspect was injured.

State police and the pair of alleged robbers exchanged gunfire at about 3 p.m. Monday on Route 153 in Westbrook after the suspects’ vehicle and a state trooper’s vehicle crashed, according to state police. Troopers were assisting Old Saybrook police, who had responded to a report of an armed robbery at the Days Inn on Boston Post Road just before 3 p.m.

In an update Wednesday afternoon, state police said that in the exchange of gunfire between the two suspects and a trooper, the trooper was shot.

State police spokesman Lt. J. Paul Vance identified the trooper who was shot as Detective Scott Wisner, a 21-year veteran officer. Wisner, who is assigned to Troop F in Westbrook, is home recovering from his injuries after being treated on Monday at Middlesex Hospital Shoreline Medical Center in Essex, Vance said.

Sgt. Keith Graham, a 14-year state police veteran who was also at the scene, has been placed on administrative leave pending the outcome of the investigation into the incident, Vance said. Graham discharged his weapon during the exchange of gunfire with the two suspects, Vance said.

The second suspect, whom police have not identified, was also injured and was taken by Life Star helicopter to Hartford Hospital for treatment of serious injuries. Police said he is expected to recover, though the nature of his injuries has not been disclosed. The injured suspect is under 24-hour state police guard as the investigation continues, Vance said.

The investigation is being led by the Office of the State’s Attorney, with assistance from the Old Saybrook police and state police Eastern District Major Crime Unit.