One person reported seeing Newell on the ground and McDowell running from the scene and a second person reported seeing McDowell and Newell arguing and yelling at each other at around 8 a.m., according to records.
Police were notified of the stabbing at 9:18 a.m., records show.
Newell was stabbed once in the left shoulder, once in his upper left body and once in the neck.
An emergency room doctor said Newell could not move part of his left leg, leading the doctor to believe Newell may have suffered a spinal cord injury, court records show.
Newell was first taken to City Hospital in Martinsburg, then airlifted to Inova Fairfax Hospital in Falls Church, Va. A hospital spokeswoman there said Monday evening that Newell's condition had been upgraded from critical to fair.
Both Newell and McDowell have faced criminal charges in the past.
According to court records, McDowell was sentenced to serve 180 days in jail earlier this year after he pleaded guilty to one count of possession of a controlled substance. He was given credit for 31 days he had already served.
Officials at Eastern Regional Jail said they could not say when McDowell was released.
Newell has faced felony and misdemeanor charges, including delivery of crack cocaine, robbery, shoplifting, destruction of property and resisting arrest, according to court records. On the most recent records, he listed his address as being in Capital Heights.
Capital Heights was the scene of a fatal shooting three weeks earlier. In that case, Kirk Leon Grantham, 25, was charged with murder in the death of Marvin Redman, 35.
Grantham was being held in Eastern Regional Jail without bail.