Authorities said Knoll, who was airlifted Friday to Wilson Memorial Regional Medical Center in Johnson City, had been on life support and died during the weekend.
Soon after deputies responded to the scene at Knoll's residence Friday morning, Norwich police arrived with the department K-9 Weeks and began tracking with a deputy.
At about 7:05 a.m., dispatchers at the 911 center received a call about a vehicle that struck a utility pole on Preston Center Road in the town of Preston, then left the scene.
A member of the Preston Fire Department located a pickup truck with front-end damage at the intersection of Preston Center Road and county Route 4, but no one was in the vicinity, deputies said.
State police responded to the crash and determined that the pickup belonged to Danielson, who was located at his home about a mile away. Danielson was taken to the sheriff's office for questioning and was arrested, Cutting said.
Danielson originally was charged Friday with attempted murder and robbery, authorities said. He was arraigned in town court on the more-serious second-degree murder charge Monday and returned to jail without bail.
McBride said Scott Clippinger of Smyrna has been appointed by the court to represent Danielson.
Clippinger didn't return a message left at his office today.
The robbery charge was lodged because some unspecified personal items taken from Knoll by Danielson, authorities said.
Knoll and Danielson had lived in Preston, but had broken up about four months ago, authorities said, and Knoll moved to Norwich.
Knoll had two other sons, ages 10 and 14, authorities said, and those boys were with their father Friday morning.
Residents in Norwich, Preston and Oxford have provided valuable assistance since Friday, Cutting said.
The investigation continues, the sheriff said, and anyone who was in the area of Maple Grove Trailer Park at about 6 a.m. Friday and may have seen suspicious activities is asked to call 337-1921.