On Better Call Saul Season 1 Episode 6, a train arrives in Albuquerque carrying Mike Ehrmantraut. He's just arrived from Philly and his daughter in law meets him at the depot. Before he leaves with her, he dresses a bullet wound in his shoulder.

Mike spends time with his granddaughter and his daughter in law and they discuss their loss. His son, her husband. She wonders how long Mike is sticking around and he tells her he's there for the duration. She remembers what her husband was like just before he died and she wonders if there was something more to his death than either of them know.

She listened as he spoke to someone on the phone at 2:30 in the morning and says she suspects he had been talking to Mike. He tells her that he wasn't the one on the phone. He leaves Stacey's house and asks his cab driver to take him to a vet so he can have his bullet wound stitched up. The vet offers to find Mike some work but mike turns him down.

In the present day, Mike sits in an interrogation room with the police from out of town. He says only one word: "lawyer." 

Jimmy shows up and Mike tells him to spill his coffee on the officer who's been taking notes. Jimmy refuses and instead asks the officers to fill him in like he didn't know anything. The officers are there investigating the deaths of two officers who were with Matty the night he died. It's clear that one of them suspects Mike of their murders. After their discussion, Jimmy spills his coffee on the younger one and Mike lifts the notebook.

After looking through the notebook, Mike makes a phone call. Stacey called the Philadelphia PD and told them she suspected Matt was dirty because she found money in a suitcase after she moved. He admits that he was the one on the phone at 2:30 in the morning and storms out.

We flash back to a night approximately six months earlier. Mike breaks into a cop car before heading inside to drink. He sees Hoffman and Fensky in the bar and tells them he knows it was them who killed his son. Mike closes the bar down that night, completely drunk, and tells the bartender he's on his way to Albuquerque the very next day. When he leaves the bar, Hoffman and Fensky offer him a ride home and after putting him in the back of the squad car, they take his gun.

Mike tells the cops he knows they killed his son and he's going to prove it.  They pull into an empty parking lot and pull Mike out of the back seat. After leaning him against a pole, they walk away to discuss how to make Mike's death look like a suicide and plan to kill him and leave him there. 

Mike was pretending to be drunk. He shoots Hoffman and Fensky and leaves them lying in the parking lot. The story flashes to the present day and Mike is telling Stacey the story of Matt's final days.