A man is claiming self-defense in a shooting that killed another man at a SEPTA train station in North Philadelphia Friday evening, police said.

Philadelphia Police Inspector DF Pace said after 7:30 p.m., a man in his 20s approached two uniformed 22nd District officers who were working outside the SEPTA's Broad Street Line at the Broad-Girard Station and told officers he shot someone on the train northbound.

The man said he was assaulted unprovoked. Officers went down to the train and found a man, possibly 18 years old, suffering from gunshot wounds, said Pace.

The man who was shot was taken to Temple University Hospital by officers and was pronounced dead at 8:09 p.m.

"The entire incident involving this shooting was captured on video cameras, SEPTA video cameras that were on the train itself," said Pace. "And what it shows is the decedent pacing up and down the railcard when it appears without any provocation whatsoever, began to strike the man who ultimately fired the weapon several times in the face, actually knocked him to the ground and continued to strike him."

The alleged shooter has a legal permit to carry and had a firearm on him, police said.

Police told CBS News Philadelphia that the man in his 20s shot at the other man at least once, but it's unclear how many shots were fired.

There were also witnesses at the scene. It's also unknown how many people were on the train at the time.

Police said the video does appear to confirm the alleged shooter's version of events.

"Based on what we see so far, we're investigating this as a case of an individual that was attempting to save himself from further serious bodily injury," said Pace.

The alleged shooter has serious injuries to his head and will be treated at a hospital. Police said the alleged shooter has cooperated with police and is at police headquarters being interviewed.

There is no motive at this time.

Police believe there wasn't anyone with the man who died. The man's identity is also unknown at this time.

"Still trying to investigate why this happened and who this person is," said Pace.

"It doesn't appear that there wasn't anything between these individuals," Pace continued. "It doesn't appear that these individuals knew each other and why this person decided to engage in violence. We just do not know at this time."

The SEPTA train northbound at this stop is suspended due to the train being part of an investigation.

"That train is remaining where it was when the shooting occurred and will not be released until the scene has been cleared," said Pace.

SEPTA police will be taking the lead in the investigation and will be working with Philly police.