Charlie Barnett Charlie Barnett

As a paramedic, Peter Mills saves lives on a nearly daily basis on Chicago Fire. But will his job cost him his own life?

In this exclusive sneak peek from Tuesday's episode (10/9c, NBC), Mills (Charlie Barnett) gets a visit from an irate father whose son died of pulmonary edema under Mills' care.

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"All I know is he went into that ambulance alive and he came out dead and that's on your a--," the father yells as things quickly turn physical. The worst part? This guy does not seem like someone to be messed with, if you catch our drift.

Check out the exclusive sneak peek to hear his menacing last words to Mills:

Chicago Fire airs Tuesdays at 10/9c on NBC.