Newly released surveillance video shows Mason earlier in the day as he tried to grab a newborn baby from its mother's arms. A Good Samaritan forced Mason away and blocked him from the woman and the child.
Mason has been booked on charges including aggravated assault on police.
Toxicology test results that were released on Wednesday revealed that Mason was not on drugs at the time of the incident. Police had already suspected the man suffered from mental illness.
It happened around 3:00 p.m. Monday on the platform at Broad and Fairmount in North Philadelphia.
Surveillance cameras captured it all as SEPTA police officer Ron Jones confronted the man. Police say the suspect claimed he had a gun.
The suspect charged at the officer, who pulled out pepper spray but it was no use.
Ofc. Jones whipped out his baton but the suspect kept coming, throwing the officer on the ground and up against the platform wall.
The no-holds-barred struggle continued as dozens of SEPTA riders ran off the southbound Broad Street train. Many were in shock.
Police say Mason even tried to get the officer's gun. It wasn't long before a few Good Samaritans rushed over to help subdue the suspect.
However, the violent encounter didn't end there.
Mason overpowered the men on top of him and ran back onto the train, where police say he tried to grab a child from his mother.
Backup finally arrived and Mason was taken into custody. Police say he did not actually have a weapon.