PHOENIX -- A convenience store security guard fatally shot one man and superficially wounded another during an apparent robbery attempt in west Phoenix, police said.

One man pointed a gun at the 67-year-old security guard around 1:30 a.m. Sunday while the other apparently went to steal items from the store, Phoenix police Sgt. Andy Hill said.

As the suspects ran away, Hill said the man with the gun pointed it at the security guard, who then fatally shot the suspect, identified as 21-year-old Daniel Arbizu.

Hill said the second suspect, identified as 20-year-old Marcos Martinez, attacked the security guard, who then shot Martinez in the arm. Hill said it was a superficial wound.

Detectives said the gun that Arbizu had been carrying had no bullets in it. Because the security guard had no way of knowing that, Hill said it did not affect his right to use deadly force.

Martinez was being held on charges of attempted robbery and first-degree murder under the felony murder rule. The rule allows prosecutors to allege first-degree murder in cases where a separate felony results in death

Clerk Brady Daniel was shot and killed during at the same Circle K on June 4, but Hill said there was nothing to suggest the incidents were related.