Garnell Morrison says a man and his girlfriend were friends of his son and they were at his house in the 900 block of 6th Street SE with other friends.
"They started fighting - the guy and the girl started fighting," Morrison said.
The Morrisons say their son and a group of his friends ran over to break it up. When they did, friends of the boyfriend and girlfriend, who were also outside, didn't like that.
"And my son says, 'Hey, we were just stopping a fight, we didn't want anyone to get hurt' while they're doing this and my son starts going back to the house and looks to see if everyone else is coming," Morrison said.
And that's when he saw one of his son's friends on the ground bleeding.
Police say the 23-year-old, who tried to protect a girl from being attacked, collapsed and died in the middle of the street.
Investigators say the attacker fled in a car with a several others. They arrested him moments later down the street and recovered a knife.
He's been identified as 24-year-old Marcus Frounfelter.
"I was very upset because this has has been a quiet neighborhood," said neighbor Shirley Ferguson. "I've lived here 16 years."
The Morrisons say their son is having tough time as one second, his friend did the right thing, and the next moment, he was dead.
Police say no one called 911 before the stabbing, only after. If they had, police say maybe they could have arrived before the worst happened.
Detectives are still trying to figure out what lead-up to the argument in the first place.