Thirty-five-year-old Antonio Santiago of Allentown had just got off work and was headed to meet a friend in the 1000 block of Turner Street when two masked assailants attempted to rob him, authorities said Monday.

The robbers pepper sprayed his face and he was pistol whipped, causing injury, Santiago reported to police.

That was then he decided to fight back, grabbing his own 9-mm handgun and fired off a single bullet that eventually killed one of the identified robbers, 30-year-old Shane Gesnaker of Williams Township, authorities said.

City officers responding to the crime scene found Andrew Eberts, 31, another identified robber, performing CPR on Gesnaker while Kaitlin Acierno, 28, the third identified robber, screaming that her "boyfriend was dead,” authorities said.

Investigators later seized a black BB handgun in a nearby trash can believed to have been used in the crime.

Eberts, no known address, and Acierno, 28, of Dublin, Bucks County, are each charged with felony robbery and felony conspiracy to commit robbery. Acierno additionally is charged with evidence tampering. Both area awaiting preliminary arraignments on the charges.

Investigators connected the pair to the alleged robbery after Gesnaker was pronounced dead at 3:41 a.m. Saturday, according to the Lehigh County Coroner’s Office. He was found outside a home in the 200 block of North Hazel, an alley near North 10th and West Turner streets. The cause of death was a gunshot wound and ruled a homicide, First Deputy Coroner Eric Minnich had said.

Lehigh County District Attorney Jim Martin and Allentown Police Chief Tony Alsleben said Monday in a joint statement the investigation determined Santiago had just parked his car when he was approached by the assailants, who forced open Santiago’s car door and demanded money, authorities said.

One of the assailants, later identified as Gesnaker, was holding the black pistol and whipped the left side of the victim’s face with it, authorities said.

Santiago reported after being sprayed with pepper spray, he told the attackers to “hold on” while he searched for cash. Santiago, who is a licensed gun owner with a permit to carry, then grabbed his 9-mm handgun and fired, authorities said. Gesnaker was struck by the bullet, fell to the ground approximately 50 feet from Santiago’s car and eventually, succumbed to injuries, according to authorities.

An investigation later determined Gesnaker, Eberts and Acierno were all allegedly involved in a plan to commit a robbery at that location. Acierno was carrying the BB gun and pepper spray, authorities said, but once Gesnaker was shot, she discarded it into a trash can near Russel and North Hazel streets.

That homicide was one of two city police investigated this past Saturday.

Christopher Sappah, 28, was pronounced dead inside his apartment on the 700 block of Walnut Street at 12:45 p.m. Saturday, according to the Lehigh County Coroner’s Office. An autopsy is scheduled sometime Monday to determine Sappah’s exact cause of death. The manner was ruled a homicide, according to the Lehigh County Coroner’s Office.

There also was an earlier, nonfatal shooting at about 1 a.m. Saturday in the 500 block of North Penn Street, police Capt. Glenn Granitz Jr. had said. The adult male victim in that incident was taken to an area hospital with injuries that were not believed to be life-threatening. Charged in the nonfatal shooting is 20-year-old Joshua Roman, who is listed in court records as an Allentown resident.

Roman was arraigned Saturday morning before District Judge Ronald Manescu on felony counts of aggravated assault and criminal trespass, in addition to reckless endangerment and carrying a firearm without a license. He was sent to Lehigh County Jail in lieu of $250,000 bail and faces a preliminary hearing before Manescu tentatively scheduled Feb. 25.

Pamela Sroka-Holzmann may be reached at pholzmann@lehighvalleylive.com. Follow her on Twitter @pamholzmann. Find lehighvalleylive.com on Facebook.