SPRINGFIELD - An armed suspect who opened fire on police and then barricaded himself in a Sumner Avenue convenience store in an early morning standoff with police is dead of an apparent suicide, police said.

Police spokesman Ryan Walsh said when officers entered the bathroom of the Sunoco station they found the suspect dead of “an apparent self-inflicted gunshot wound.”

The man’s identity has not yet been disclosed to the press.

Walsh said police were called to the area of 700 Sumner Avenue at around 3 a.m. after receiving an alert from Southbridge police. The man had apparently been involved in some kind of domestic altercation in that town. He was reported to be armed and threatening to take his own life.

Officers spotted the man inside the Sunoco at 730 Sumner Ave. by the front counter. When they entered the store and approached, he drew a gun and opened fire at officers, Walsh said. Officers returned fire and he retreated into the store’s bathroom.

The cashier was unharmed and was escorted out to safety.

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With the suspect barricaded inside the bathroom and no one else in danger, officers called for the department’s Emergency Services Unit, a tactical team, to the scene.

When tactical officers entered the bathroom around 90 minutes after the exchange of gunfire, they found the man dead. The gun was located inside the bathroom, as was a quantity of heroin, Walsh said.

The man had also been struck by gunfire in the shootout with police, he said.

The station remained closed Tuesday morning and cordoned off with crime scene tape. The police forensics van was parked inside, and detectives could be seen searching through the accumulated snow with a metal detector.

Several evidence markers could be seen in the parking lot between the pumps and the front door.

The incident is under investigation by the Springfield Police homicide unit and the Hampden District Attorney’s Office.