It happened just after 6:30 a.m. on 22nd, near Diamond Street.
Officials say Medic 50 was dispacted just after 6 a.m. to pick up a person on 18th and Ridge Avenue. Two fire service paramendics picked up the individual and put him in the back to take the man to Temple hospital.
One medic was in the back with the patient, while the other medic was driving. The driver told police they saw a tussle in the back of the ambulance and pulled over near 22nd and Diamond streets.
When he opened the door to check on what was going on, the man ran away. That's when he noticed his partner had been stabbed in the right and and side of his chest. Officials say the medic may have also been bit.
The partner immediately began helping the injured medic and called police for help.
The medic was rushed to the hospital by police and is said to be in serious condition. He is expected to make a full recovery.
WATCH: Officials give update after medic stabbed
Officials give update after Philadelphia medic stabbed while on emergency call
The suspect was taken into custody at 23rd and Norris streets.
The fire commissioner spoke about how the department makes around 1,000 runs per day trying to help people.
"It is unfortunate because first responders -- what we do everyday is attempt to make people's lives better and it's one of those things you can't predict," said Philadelphia Fire Commissioner Jeffrey Thompson.
The fire department says it is standard procedure to have two medics responding to a call.
Police are talking to witnesses and continuing to investigate.
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