On Monday, Tywain Robinson told jurors about frequently seeing the victim with a gun, and how their relationship took a negative turn.
Robinson says he feared for his life when he shot and killed 24-year-old Isaac Jackson.
Robinson - accused of murder and attempted murder - on the other side of the courtroom Monday, testifying in his own trial.
He told jurors about the moment two men showed up at the doorstep of his Southeast Fresno apartment in May of 2021.
"I was feeling scared," said Robinson. "I honestly thought I was going to be shot or killed."
Robinson then opened fire from inside the home, killing Issac Jackson and shooting at Jackson's friend, Terrell.
Both men had gone to the apartment to check on Robinson's partner, who is also the victim's niece.
Investigators say there's no evidence anyone else had a gun, but Robinson testified otherwise.
"I seen Isaac in front of the door with no shirt, and he also had a gun in his hand," said Robinson.
Robinson also told the jury he had always known Jackson to have a firearm on him - including during a prior encounter with his partner's family in Palmdale.
"He pulled his gun out and made it seem like if I didn't leave, he was going to shoot me." said Robinson.
But during the day in question - Robinson also recalled the argument he had with his partner and her mother in the morning.
"She told me that she was going to send someone to my house to kill me," said Robinson.
And that's why he says he opened fire on Jackson and Terrell.
"I thought they were making their way in so, I fired once at the door and twice at the wall," said Robinson.
Cross-examination is expected to start Tuesday, and there could still be more testimony.
Then jurors will decide if this was a case of self-defense or murder.
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