A Cobb County jury took 30 minutes to convict a man who strangled his grandfather and then drove around town in the dead man’s truck with his body inside.

Casey Ryan Collins was convicted of malice murder, felony murder, four counts of armed robbery, two counts of aggravated assault, and concealing a death in the May 2013 death of Edward ‘Ron’ Smith, the Cobb District Attorney’s Office said.

Smith, 78, was stabbed and strangled inside his truck and then robbed of his wallet, according to investigators.

“This strangulation was so brutal that the belt tore a rip in that man’s neck and broke a vertebrate,” Deputy Chief ADA Michael Scott Carlson told jurors. “This was one of the people who gave Casey Collins life, and the defendant chose to bring him death.”

When other family members couldn't reach Smith, Collins and his then-girlfriend, Sarah Elizabeth Cook, claimed they, too, were worried about the man, The Atlanta Journal-Constitution previously reported.

“They were upset,” Tammy Smith Connor, Collins’ mother, said. “They acted just like they were worried just like we were.”

Smith’s disappearance was reported to Cobb police, and two days later, Smith’s truck was found with his body still inside. Investigators determined that Collins and Cook had driven around the metro area and shopped using Smith’s wallet. After abandoning the truck, the pair had called a cab to come pick them up in the same area, investigators said.

Both Collins and Cook were initially charged with murder for Smith’s death. But in October, Cook pleaded guilty to armed robbery and aggravated assault and is serving 15 years in state prison with no parole, to be followed by 10 years on probation.

Cook testified against Collins at his trial. Prosecutors told the court that Collins wanted to kill his grandfather for not supplying him prescription pills as he had done in the past, the DA’s office said.

Sentencing for Collins has not yet been scheduled.