LOS ANGELES (CNS) — A 20-year-old man accused of gunning down an off-duty Monterey Park police officer during what the district attorney called a botched robbery attempt in Downey made an initial court appearance Thursday and was ordered to remain jailed without bail pending a September arraignment.

Carlos Delcid appeared in a Downey courtroom, but his arraignment on charges of murder, attempted robbery and being a felon in possession of a firearm was delayed until Sept. 8. The case was transferred to the Norwalk courthouse.

The murder charge includes a special-circumstance allegation of murder during a robbery, and District Attorney George Gascón — who opposes the death penalty — says Delcid is facing a possible sentence of life in prison without the possibility of parole.

According to jail records, he was arrested around 9:30 p.m. Monday, roughly six hours after the shooting that killed Officer Gardiel Solorio, 26. A 17-year-old suspect was also arrested for allegedly acting as the getaway driver, Gascón said during a Wednesday afternoon news conference. That suspect, who was not identified, is being charged in juvenile court, and the exact charge or charges were not immediately clear.

A 17-year-old suspect who was allegedly driving the pair's getaway car was also arrested, Gascón said. According to the District Attorney's Office, the unidentified teen was charged with a single count of murder in Compton Juvenile Court. On Thursday, the teen denied the petition — the equivalent of a not-guilty plea in adult court, according to prosecutors. He is due back in court Sept. 14.

Solorio was in his vehicle in the parking lot of an LA Fitness gym in the 12700 block of Lakewood Boulevard around 3:30 p.m. Monday when Delcid allegedly got out of a car nearby and approached Solorio "with a gun drawn in what appeared to be an attempted robbery," the district attorney said.

"Officer Solorio attempted to flee by backing up his vehicle when the suspect fired multiple times," Gascón said. "The defendant then returned back to the vehicle where a juvenile was behind the wheel and they fled the scene."

Solorio was found unresponsive in the seat of his car, and was pronounced dead at the scene, according to Downey police.

Funeral arrangements were still pending for Solorio, a rookie officer just weeks out of the academy. Monterey Park Police Department Chief Kelly Gordon called his killing “a senseless act of violence.”

Gordon said at a Tuesday afternoon news conference that Solorio, who grew up in Bell Gardens and graduated from Cal State Los Angeles with a degree in criminal justice, joined the department as a recruit in January, and had just graduated from the sheriff’s training academy on July 22 before beginning his field training on July 25.

"Although his time with (the department) was very short, we all knew from the moment we met him that he had the heart of service and was going to be a great officer," Gordon said.

"And I could tell that from the moment he walked in and did our first introductions in my office. The family and department are grieving right now, and this is an especially difficult tragedy. It's a senseless act of violence. He was only 26 years old. I don't know about all of you, but I have children that age. So to me this is particularly difficult."

Solorio is survived by his parents, brothers, sisters and fiancée.

His fiancée and one of his sisters attended the Wednesday news conference when the charges against Delcid were announced.

On a GoFundMe page established to help cover expenses for family to attend his funeral, Solorio's sister-in-law, Wanda Marie Lane Solorio, wrote that it was his "lifelong dream" to be a police officer.

"His dream of becoming a police officer after years of hard work and dedication had finally come to fruition, when life was abruptly taken away due to a senseless act of violence," she wrote. "He was taken from his family way too soon. He was and has always been true American success story."

She said Solorio was the youngest of 13 children, and the family is hoping to raise money so all of his brothers and sisters can attend his funeral.

As of Thursday afternoon, the family had raised more than $16,000.

"(He) was a first generation college graduate, and the first and his family to become police office and brother in law enforcement," Wanda Marie Lane Solorio wrote.

The arrest of Delcid has again led to criticisms by opponents of Gascón, who are seeking to have him recalled from office, claiming his policies against filing sentencing enhancements in criminal cases allowed the suspect to avoid extended jail time earlier this year.

Critics said Delcid should have been behind bars from a criminal case filed in February, in which he was charged with burglary, domestic violence, assault, false imprisonment and witness intimidation.

According to court records, he pleaded no contest to the burglary and domestic violence counts and was sentenced on March 10 to four years' probation and 180 days in jail. Jail records indicate he was released from custody the next day, with credit for time already served.

Critics said if Gascón had allowed prosecutors to file a sentencing enhancement for the use of a knife in the case, Delcid may not have gotten such a lenient sentence and might still have been behind bars.