She snapped two photos of the snake before chasing after it with a shovel in her hands.
"I saw it take off and I was like, 'This animal can't be here. It's a poisonous reptile,'" she told WPVI. "I can't have a poisonous snake. There (are) little kids here."
Animal control experts later confirmed the snake was a 4 1/2-foot Asian cobra, KYW-TV reported.
"I was just concerned for everybody else, because not everyone would know," Kehoe told WPVI.
The news station reported Kehoe believes the snake might have been roaming her apartment complex for months before Monday's encounter. Authorities removed 20 venomous snakes from another apartment in her complex in March, according to The Associated Press. Officials were not certain the snake had escaped from that roundup, the AP reported.
Wildlife experts recommend that anyone who sees a venomous snake leave it be and call authorities.