Sanitation workers doing garbage pickup four years ago in an alley in a Phoenix neighborhood made a gruesome discovery: A 6-year-old boy was found shot in the back of head, less than a day after his father suffered a similar death on his living room sofa.

Authorities say Xavier Jaquez was likely killed because he either saw or heard his father get killed in December 2010 over a drug dispute. Xavier kicked and screamed as his uncle pulled him away, forced him into a car and drove to the alley 20 miles away, police said.

"I wanna be with my dad, please let me go," Xavier was quoted as saying by a neighbor who witnessed the child's resistance.

Opening statements at the trial of Christopher Rey Licon are scheduled to be held Wednesday. The 24-year-old is charged with fatally shooting his half brother Angel Jaquez at their Phoenix townhome. He also is charged with kidnapping and killing the child and breaking into an apartment where he is accused of stashing a handgun believed to have been used in the crimes.

Prosecutors are seeking the death penalty against Licon, who has pleaded not guilty to the charges. His lawyers tried unsuccessfully to have death penalty taken off the table due to mental illness that they say he had at the time.

Licon, then a construction management student at Arizona State University, told investigators that he was studying at a library in Tempe at the time that his half brother was killed. He said he came home to find his brother's body on a sofa in the townhome that they shared.

But authorities say Licon's alibi collapsed quickly after neighbors were interviewed and other evidence was gathered.

Investigators believe Jaquez was shot in the back of the head as he watched TV, and the child was in the home when the killing happened.

Authorities say two key pieces of evidence were found inside the car Licon used to bring the boy to the alley: a 9 mm bullet casing that matched a casing found at Jaquez's home and a toy from a Burger King kid's meal.

Xavier was found in the alley next to a Burger King kid's meal that was missing its toy.

Prosecutors say Licon was in an illegal drug business with his half brother and had acknowledged selling drugs in the months preceding both deaths.

They also said Licon, while in jail awaiting trial, told his cellmate that he shot Jaquez in anger during a fight over drug profits. Police say they found drugs inside a cupboard at Jaquez's townhome.

Licon's attorneys have questioned the credibility of the cellmate, who was sentenced to 10 years in prison for guilty pleas to child abuse charges. Police say the cellmate took part in a plan to give his 2-year-old son a mixture of methadone and Kool-Aid to relieve his tooth pain. The child overdosed but survived.

Licon's attorneys say there's no evidence that Xavier witnessed his father's death. They also said there were no signs of bad blood between the two brothers and that Licon had a psychotic episode around the time of the killings.

Prosecutors disputed that Licon was insane at the time.