EL CAJON, Calif. -- A young man shot and killed a teenager in Murrieta for no reason, then murdered a 7-Eleven clerk in eastern San Diego County during a robbery about 24 hours later, a prosecutor told a jury Monday.

Deputy District Attorney James Romo told jurors in his opening statement that there is overwhelming evidence to find Samuel Thomas "Tommy" McCauley Jr. guilty of murder charges in both shootings.

The defendant is accused of gunning down 18-year-old Duante Mercado-Bates on a Murrieta street just after midnight on Nov. 24, 2006, and 7-Eleven store clerk Pedro Hernandez Vargas about 2 a.m. the following morning in Lemon Grove.

McCauley, 24, is also charged with attempted murder for allegedly shooting a customer, 19-year-old Andre Villaverde, in the face during the 7-Eleven robbery.

The defendant -- who is also charged with robbery and attempted robbery charges -- could face the death penalty if convicted of murder and the special circumstances of murder during a robbery, murder during a burglary and multiple murders.

Co-defendant Franko Bernal, 22, is charged with the same crimes and could also face the death penalty if found guilty. Opening statements in his trial are scheduled Tuesday at the courthouse in El Cajon.

Both juries will hear some of the evidence against the defendants at the same time.

Romo told the jury in the McCauley case that Mercado-Bates stayed home when his family traveled to Orange County on Thanksgiving Day, Nov. 23, 2006.

The victim -- who didn't have a car and was known to walk around the neighborhood -- wasn't home when the family returned about 8:30 p.m., Romo said.

"Duante Mercado-Bates didn't come back that night," the prosecutor told the jury.

A passerby spotted his body lying on a street in a planter about 6:30 the next morning and called police, Romo said. There were no signs of a robbery, and the victim was still clutching a bag of corn nuts in his hand, the prosecutor said.

The victim had two bullet wounds -- one to the upper body and one to the left side of his chest -- but no other signs of trauma were found, the prosecutor said.

Two .22-caliber casings were located next to the body, but there were no witnesses to the crime, Romo said.

A security video camera at a nearby business captured Mercado-Bates walking by at 12:13 a.m, the prosecutor said.

A little more than 24 hours later, a 7-Eleven security camera captured McCauley shooting the 54-year-old Hernandez Vargas three times in the chest during a robbery just after 2 a.m., Romo said.

He told the jury he would show them the video during the trial.

"You, as jurors in this case, are going to see a murder," the prosecutor said.

Romo said Villaverde, a clerk at a nearby supermarket, was stopped at a traffic light before the robbery and noticed a passenger tumbling out of a car in the street.

The passenger and the driver appeared to be arguing, then they both got back in and took off, the prosecutor said.

A few minutes later, Villaverde was in the 7-Eleven paying for drinks when a black-hooded figure came in with a gun raised and shouted "Give me the money. Give me the money," according to the prosecutor.

Villaverde was shot in the face but was able to drive back to the supermarket and call 911, Romo said. The robber then turned his attention to the clerk, Hernandez Vargas, and shot him three times in the chest, the prosecutor alleged.

"The robber didn't even give him a chance to do anything," Romo told the jury.

The robber can be heard in the surveillance video saying "Open it. Open it. Open it," the prosecutor said.

After McCauley shot the clerk, he was heard to say, "Shut up bitch, I didn't hurt you that bad," according to Romo.

McCauley used a .22-caliber sawed-off rifle to smash the doors to a cooler and tried to steal two 12-packs of beer, but dropped one of them and took a third 12-pack, the prosecutor said.

The defendant's fingerprint was later found on the 12-pack left behind, Romo told the jury.

Villaverde later told detectives that the gunman was the same man who fell out of the car in the street, Romo said.

A man called Crime Stoppers and said the defendant came to a friend's house on Nov. 25, 2006, boasting about killing a clerk and killing a "kid" in Murrieta, according to the prosecutor.

The tipster said McCauley told his friend that "killing got his rocks off," Romo alleged.

Experts determined that casings recovered from the 7-Eleven store were fired from the same rifle as casings found at the Murrieta murder scene, Romo said.

A mutual friend told authorities that Bernal had a sawed-off .22-caliber rifle that was known as "Jack Sparrow" because it looked like a pirate gun, the prosecutor said.

Romo said another witness told authorities that Bernal and McCauley showed up at a friend's birthday party on Nov. 24, 2006, and McCauley told her "I killed a kid in Murrieta last night."

Bernal thought the comment was funny and said "Clack, clack, clack," to imitate the sound of a gunshot, Romo said.

Another person at the party said McCauley was drunk when he was telling people about the shooting, the prosecutor said.

"He (the witness) said Tommy said he was going to do 'something that night,'" Romo told the jury, referring to the robbery/murder at 7-Eleven.

Twenty-four hours after the murder in Murrieta, McCauley sent a message to Bernal that was posted on Bernal's MySpace page that read "Clack, clack, clack," Romo said.

The prosecutor said Bernal was arrested a week after the murders, but McCauley took a bus to his aunt's home in Cody, Wyo., where he told her that he had killed two people.

When asked why, McCauley said "No reason," according to the prosecutor.

The defendant said there was a third person in the 7-Eleven who survived the gunfire, a man who ran into the cooler to avoid being hit, the prosecutor said.

When McCauley's aunt saw the 7-Eleven video, she said, "That's Tommy," according to the prosecutor.

A friend will testify that he saw Bernal acting tough at the Nov. 24 birthday party, showing off a gun stuffed down his pants, Romo said.

Two ex-girlfriends will also testify that Bernal was known to put the gun down his pants, the prosecutor said.

On Dec. 20, 2006, McCauley told his father in a jail-recorded call that he would have to "reap what he has sown," the prosecutor said. The defendant's father told his son that he knew it was him in the 7-Eleven surveillance video, and the son didn't deny it, Romo said.

McCauley said he was drunk when he committed the robbery/murder, the prosecutor alleged.

Defense attorney John O'Connell asked jurors to keep an open mind and listen to all the evidence before deciding his client's fate.

O'Connell told the panel there were no witnesses to the murder in Murrieta, and he doubted the prosecution could prove its case beyond a reasonable doubt.

"They don't have any motive for what happened," O'Connell said. "They don't know why. There's a lot they (authorities) don't know."

There was a lot of drinking at the birthday party in question where McCauley supposedly talked about "a shooting up north," O'Connell told the jury.

It was also unclear whether Bernal or McCauley made the incriminating statements, O'Connell said.

He said it was clear that McCauley was extremely intoxicated and was on a several-day drinking binge around the times the murders happened.

O'Connell said the 7-Eleven surveillance video was blurry, and contended that Villaverde identified Bernal as the person who shot him in the store from four feet away, saying McCauley was outside in the car.

The attorney said McCauley was upset when he arrived at his aunt's home in Wyoming and "wanted it all to end."

Witnesses made statements to authorities to cash in on reward money offered by different organizations, O'Connell alleged.