Midnight murder

The midnight train is coming down the mountains. Art Farnanski seems to be dozing off in his seat. Someone knows that this is not true. At the station, all the passengers get off the train, except one. The conductor comes and taps him on the shoulder to let him know they have arrived. Art Farnanski does not answer. He is dead. Hours later the four people that had shared the train compartment with the dead man are at the police station.

The man in the dark suit:
"I'm innocent. The blonde woman was talking to Farnanski."

The blonde woman:
"I'm innocent. I did not speak to Farnanski."

The man in the light suit:
"I'm innocent. The brunette woman killed him."

The brunette woman:
"I'm innocent. One of the men killed him."

That same morning, while he is serving him coffee, the waiter at the Petit Piccolo asks the commander. This is an easy case for you isn't it?

Yes, answers the commander. "Four true statements and four false ones. Easy as pie."

Who killed Farnanski? (only one person is guilty).