ST. LOUIS — A St. Louis mother fell to the floor after getting heartbreaking news Tuesday morning.

She learned her youngest daughter, 23-year-old Brianna Laster, died after she was stabbed repeatedly on I-70 Monday.

RELATED: Man charged with murder in fatal I-70 stabbing

Kim Laster said she spent years trying to save Brianna from the grips of heroin addiction. She said Brianna had been fighting addiction for about three years. 

Derrick Sanders Jr., also 23 years old, admitted to police that he stabbed Laster after an argument in a car. Kim Laster said she thought the two met for the first time Monday at a store.

“They drove off, I guess they were getting high," she said. "They got in an altercation he stabbed her she climbed out the back seat ran across the highway and got on somebody's porch.” 

Police say Laster got out of the car on I-70 in the Jennings area, climbed a fence and ran to the nearest house for help. The woman who answered the door tried to comfort Laster in her final moments, but Laster was pronounced dead shortly after at a nearby hospital. 

Police found Sanders at a different hospital with a knife wound to his hand. The inside of his car was covered in blood, police said. Sanders told investigators he met up with Laster Sunday night and stabbed her after a fight. 

Sanders is facing charges of first-degree murder and armed criminal action. He’s being held without bond.

A Go Fund Me page has been set up to help Brianna’s family, you can visit it by clicking here.