Authorities say the 43-year-old victim was shot twice Tuesday night while preparing to leave for work.
Investigators are working to track down four male suspects connected to the attack.
The incident took place just before 10 p.m. on the 300 block of Earlham Terrance.
Initially, police reported the shooting stemmed from an attempted robbery, but later said it was an attempted carjacking. The victim had also earlier been identified as an off-duty corrections officer; he was later confirmed to be a security guard.
Police say the 43-year-old plainclothes guard had tried to take his car to work, but it wouldn't start. As he walked to his wife's car, police say four males approached, two went one way and two went another.
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At least one of the suspects was armed.
Police say the guard, who was also armed, went for his gun.
According to police, at least one of the suspects told him 'don't do it.'
That's when shots were fired from the guard and the males.
During the shootout, police say the guard's gun malfunctioned. Earlier police reports suggested the guard's gun was struck by gunfire and became disabled, but that was not the case.
Police say the guard was shot once in the left shoulder and grazed in the forehead. He was taken to an area hospital where he was placed in critical but stable condition.
The guard's gun was recovered at the scene.
"The gentleman is a nice person and I'm really surprised this happened here," neighbor Robert Haz said.
Neighbors tell Action News they heard the gunfire and are now left on edge.
"The violence is encroaching us so closely, it's scary but I still love it here," Germantown resident Nancy Jackson said.
The guard's vehicle and another unattended parked vehicle were hit by gunfire.
No other injuries were reported.
Police continue to search for the suspects. Investigators have obtained video they are hoping will help identify them.
Anyone with information is asked to call police at 215-686-TIPS.