ST. LOUIS — A man is facing charges after he admitted to fatally stabbing a woman after an argument.

St. Louis County Police said they found Derrick Sanders Jr., 23, at a hospital with a knife wound to the hand. Police said he was driving in a car covered in blood and admitted to the stabbing in an initial interview. 

In a later interview, he told police he met the woman Sunday night. He said he stabbed her after an argument, according to police.

He was charged with first-degree murder and armed criminal action and is being held without bond.

The victim has not yet been identified, but a Jennings woman says she will never forget her face.

Erica Wheeler said she woke up to a “boom” at 3:30 a.m. Monday. There was a woman banging on her door.

At first she thought it was a burglar trying to get into her home in the 5200 block of College Avenue—until she looked through the peephole.

“I knew there had to be something wrong from that knock, that beating. That was a help knock,” Wheeler recalled.

WATCH: Woman describes opening door to I-70 stabbing victim

She couldn’t tell exactly what was going on or how hurt the woman was, so she called 911 and waited.

“She wasn’t standing up. She was on her knees and she was banging, I thought it was a kid because she wasn’t fully standing up,” Wheeler said.

But Wheeler couldn’t stand by while the woman continued to scream for help. Despite her husband’s pleas, she opened the door to help the woman.

“I opened up the door just to reassure her, ‘You’re OK, you knocked on the right door,’” Wheeler said.

Police arrived at the same time.

Emergency crews rushed the woman to the hospital, but all efforts to save her life failed. She was pronounced dead.

Several law enforcement agencies responded to the scene. After speaking with Wheeler, their investigation led them from the neighborhood along I-70 onto the interstate itself.

I-70 fatal stabbing
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St. Louis County police detectives believe it’s possible the woman was stabbed on I-70 near the Jennings Stations Road exit. Investigators shut down all westbound lanes in the area for several hours during the Monday morning rush while they searched for evidence.

If the woman was stabbed on I-70, getting to safety meant running off the interstate, climbing a fence and finally making it to Wheeler’s doorstep.

Wheeler said she can still see the woman outside of her home pleading for help.

“She was on her back taking her last breath,” Wheeler said. “Her face will always be with me. I can see her face right now, and I know she will always be with me.”

Wheeler said she knows she made the right decision in opening her front door to a stranger who was calling for help.

“I’m a praying woman. My faith is strong. That’s the decision I made; I did what I had to do.”

The St. Louis County Police Department’s Bureau of Crimes Against Persons is handling the investigation.