O'Bryan poisoned his son in order to claim life insurance money to ease his own financial troubles, as he was $100,000 in debt.

O'Bryan lived with his wife, Daynene, in Deer Park, Texas, with their son Timothy and daughter Elizabeth (born 1969).

[5] He eventually caught up with the group and produced five 21-inch (530 mm) Pixy Stix, which he would later claim he was given from the occupant of the house that had not answered the door.

Numerous parents in Deer Park and the surrounding area turned in candy their children got from trick or treating to the police, fearing it was laced with poison.

The police did not initially suspect O'Bryan of any wrongdoing until Timothy's autopsy revealed that the Pixy Stix he had consumed was laced with a fatal dose of potassium cyanide.

[14] All five of the Pixy Stix had been opened, with the top two inches (51 mm) refilled with cyanide powder and resealed with a staple.

Melvin was an air traffic controller at William P. Hobby Airport and did not get home from work until 11 p.m. on Halloween night.

[4] As their investigation progressed, police learned that Ronald O'Bryan was over US$100,000 (equivalent to about $620,000 in 2023) in debt and had a history of being unable to hold a job.

[21][22] At the time of his arrest, he was suspected of theft at his job at Texas State Optical and was close to being fired.

[1][23] Police discovered that O'Bryan had taken out life insurance policies on his children in the months preceding Timothy's death.

One month before Timothy's death, O'Bryan took out additional $20,000 (equivalent to about $123,600 in 2023) policies on both children, despite the objections of his life insurance agency.

Police also learned that on the morning after Timothy's death, O'Bryan had called his insurance company to inquire about collecting the policies he had taken out on his son.

After learning that O'Bryan had visited a chemical supply store in Houston to buy cyanide shortly before Halloween 1974 (he left without purchasing anything after learning the smallest amount available to purchase was five pounds), police began to suspect that Ronald O'Bryan had laced the candies with poison in an effort to kill his children to collect on their life insurance policies.

Friends and co-workers testified that in the months before Timothy's death, O'Bryan showed an "unusual interest" in cyanide and spoke about how much it would take to kill a person.

[35] According to Reverend Carroll Pickett, a former chaplain who worked for the Texas Department of Criminal Justice, O'Bryan was shunned and despised by his fellow death row inmates for killing his child and was "absolutely friendless".

The inmates reportedly petitioned to hold an organized demonstration on O'Bryan's execution date to express their hatred of him.

[6] Judge Michael McSpadden scheduled a third execution date for October 31, 1982, the eighth anniversary of the crime, and he offered to personally drive O'Bryan to the death chamber.

The Supreme Court delayed the date yet again to give O'Bryan a chance to pursue an appeal to seek a new trial.

O'Bryan's lawyer sought a fourth stay on the basis that lethal injection was a "cruel and unusual punishment".

[40] His last meal consisted of T-bone steak (medium to well done), French fries and ketchup, whole kernel corn, sweet peas, lettuce and tomato salad with egg and French dressing, iced tea, sweetener, saltines, Boston cream pie, and rolls.