By Walt Hunter

PHILADELPHIA (CBS) – A suspect carrying several weapons, including an AK-47, was arrested Tuesday evening aboard a Broad Street train, crowded with rush-hour commuters, at the Fairmount Station.

In addition to the AK-47 assault weapon with a magazine carrying 40 live rounds of ammunition, authorities say the suspect had on him a .38 revolver and a 12-inch bayonet knife.

Police say a passenger, who is being hailed as a hero, alerted police that a man carrying weapons had just boarded the northbound subway train at City Hall.

SEPTA police officers immediately took action, racing two stops ahead to the Fairmount Station, then boarding the crowded train, looking for the suspect.

Minutes later, police say they found Jermal Ponds sitting in the last car.

SEPTA officers Felix Adorno, Richard Galanti and Andrew Maull immediately removed Ponds from the train, and searched a black bag he was holding.

Inside the bag, in addition to the weapons, police say they found $700 cash, seven containers of suspected marijuana and 22 Percocet pills.

Records show Ponds has a prior weapons arrest for allegedly firing three shots at his ex-girlfriend in September 2011, then severely beating her. The charges were withdrawn after a witness failed to appear.

Police say they have no idea what Ponds may have been planning to do with the powerful weapons. The AK-47, officers say, was partially dismantled so it would not be visible in the bag.

Ponds allegedly told investigators that he was “heading home on the subway.”

For now, however, he’s heading to jail, held in $100,000 bail, as investigators try to determine where he got the weapons.

The suspect, they add, had carved and written his initials on both guns, apparently as proof of ownership.