It happened around 9:00 p.m. on July 2nd inside the Church Street station in the Frankford section of Philadelphia.
Police say the suspect grabbed the victim by the neck and went through his pockets, taking his wallet.
"Totally unacceptable. This was a very dangerous situation. You're talking about being in a steel box," said Jerri Williams of SEPTA.
The attack on the 86-year-old man happened while the victim was taking the elevator up to the westbound platform of the El on the Market Frankford line.
Cameras caught the suspected robber barely catching the elevator. He sized up the victim while playing with his phone.
Seconds later, as the door was opening, he made his move.
"He grabbed him by this throat and went through his pockets, even pulling down his pants as he struggled with him to get his wallet out of his pocket," said Williams.
SEPTA said, after the thief stole the man's wallet containing his ID and $500 in cash, the victim was forced to stare down his attacker as the man waited for the door to reopen.
Once the elevator reached street level, another camera captured him running off.
The victim, who possibly suffers from dementia, stumbled out looking for help.
SEPTA investigators say the victim was not seriously injured from the attack, but because of his health issues, he hasn't been able to help them much."It's crazy. They're on drugs. They want instant money from people. They need to be locked up right away," said Gail Dixon. "This is very good video, very good pictures of this man and somebody knows who he is. We're hoping, as in the past, the public is going to call in and tell us who he is and where he is and we're going to go get him," said Williams.
SEPTA says the detective asking anyone with information that could help them identify the suspect to call 215-580-3486.