MIDWEST CITY, Oklahoma - Midwest City Police have released the possible motive in a deadly weekend shooting.

Kenneth Walker, 51, was shot to death when he went to check on his 30-year-old wheelchair-bound son, Antonio Walker. Police now believe this was a robbery involving prescription drugs that the victim's son owned and that this was not a random crime.

“When you know the circumstances surrounding the homicide, then you realize it wasn't just a random act,” said Midwest City Police Chief Brandon Clabes.

Investigators said Antonio Walker was the target.

Antonio told police his friend, Sharmain Stelly, came to visit early Saturday morning. Police believe Stelly was going to Walker’s home to buy prescription drugs.

“It appeared to be involving a drug transaction because she knew that Antonio was prescribed prescription medication and had sold drugs in the past,” Clabes said.

Stelly brought her cousin, named "T.O." or "Tiny Ounce" to Antonio's house.

“At that time, apparently T.O. had started to pistol whip Antonio, pulled him out of his wheelchair and it was a robbery,” Clabes told News 9. “They were going to steal his drugs and his money.”

That is when Kenneth heard the scuffle, went to check on Antonio in his bedroom and he was shot dead.

Police said Stelly and T.O. got into a getaway car with Chakara Redd and Larry Mathis. Police have now arrested Redd, Mathis and Stelly on murder and armed robbery charges.

Stelly was actually arrested for shoplifting at Wal-Mart about 15 minutes after her murder arrest warrant was signed. They are still looking for T.O. for murder and armed robbery complaints.

The Oklahoma City Police Gang Unit helped Midwest City Police identify T.O. as Mosi Abasi Dennis.

Antonio Walker is a paraplegic after police said he was shot by another metro police agency while committing a felony back in 2006. Now, police think he may have been selling prescription drugs.

“As a result, that may have possibly led to his father's untimely and tragic death, so it's a sad case,” Clabes said.

Clabes said it is unclear at this point whether Antonio will face charges since his dad died during an alleged drug deal.