Prosecutors described both suspects as reputed gang members who were out to get revenge when they allegedly shot Valadez.
Emotions were high in court as their family members fought back tears.
Relatives of the two suspects shielded their faces as they left court on Wednesday afternoon.
The judge ordered that Shawn Gaston, the alleged gunman, and Kevin Walker, who admits to driving the car used in killing Officer Alejandro Valadez, be held without bond.
Prosecutors said gunshot residue and ballistics evidence linked the two reputed gang members to Monday's fatal shooting of Valadez in the Englewood neighborhood.
Police say Gaston and Walker had been fired upon earlier by rival gang members and had returned to the scene seeking revenge. Valadez was shot in the head and leg.
Within minutes of the shooting early Monday morning, police found a car parked nearby. On Wednesday in court, prosecutors said three guns were found inside it -- a 40-caliber handgun, a 357 revolver and a 9 millimeter carbine rifle in the trunk.
Police say ballistics tests matched the 40-caliber handgun to the bullet that struck Valadez in the head.
"He was doing what he loved to do," said Supt. Jody Weis, Chicago Police.
Chicago Police Superintendent Jody Weis joined Cook County State's Attorney Anita Alvarez after the bond hearing. Both called the shooting of Valadez, a three-year member of the Chicago Police Department, a wakeup call for common sense gun laws.
Gaston and Walker are both convicted felons. Gaston was convicted for aggravated unlawful use of a weapon -- a felony -- but was sentenced to two years probation.
Alvarez says last month, Illinois lawmakers turned down a bill her office had drafted that targeted known gang members and would have kept Gaston behind bars.
"What I was proposing was that known gang members caught on the street with a loaded weapon, be charged with a class two felony, non-probational," said Anita Alvarez, Cook County State's Attorney.
Police say Gaston and Walker have given videotaped statements. But Kevin Walker's older brother doesn't believe it. Walker says police have not allowed his brother to see the family's lawyer or place a phone call. And he fears his brother was coerced into making the videotaped statement police say they have from Walker and from Shawn Gaston, the alleged gunman in the cop killing.
"No, I don't believe it. We've seen it over the years, they can get you to say whatever they want you to say with the right amount of pressure," said Terrance Walker, suspect's brother. "They tried to paint the picture like he's a cold blooded killer, and I know my little brother. He's not like that,"
Both Walker and Gaston were on probation at the time of the shooting. Their next court hearing will be on June 8 for violating their probation.
Charged with one count of first degree murder, one count of murder of a peace officer and one count of attempted murder, if convicted both men would qualify for the death penalty.
Despite their story, police say that the suspects knew they were shooting at an officer. Kevin Walker, 21, and 20-year-old Shawn Gaston are now both charged in connection to the murder of officer Alejandro Valadez. Police say Walker admitted to driving the car. Gaston confessed to firing the fatal shots, police say.
Investigators say the two had gone to West 60th and South Hermitage looking for payback against rival gang members who earlier shot at them. Instead, they allegedly fired on Valadez. The 27-year-old officer and his partner were investigating reports of shots fired in the neighborhood. Valadez was in plainclothes but recognizable as an officer, officials said.
Police say they tracked down the two suspects a short time after Valadez was shot in the head and leg.
"At this point in time, Officer Valadez with his star out and his vest on, was talking to a citizen out in front of that house. He was fatally struck by gunfire," said Tom Byrne, chief of detectives, Chicago police.
Police say they found the car used in the shooting parked near West 61st and South Paulina. In the trunk were three guns, including what police believe was the murder weapon.
Neighbors say Gaston lives down the block from where the car was found.
"It gives part of the closure process to the families. It's a heinous crime and I'm just really pleased the way the investigation progressed," said Chicago Police Superintendent Jody Weis.
Gaston, of the 6200-block of South Paulina, and Walker, of the 2500-block of West 70th St., were each charged with one count each of first-degree murder, first-degree murder of a peace officer and attempted first-degree murder.
Valadez is the third officer killed in the line of duty in the past year.
Officer Valdez and his partner were responding to a call of gunfire when someone inside a vehicle fired at the patrol car on Monday around midnight. Valadez was pronounced dead several hours later at John H. Stroger Jr. Hospital of Cook County Monday afternoon.
Just 20 minutes after the shooting, police say they tracked down the suspect's vehicle.
Minutes after that, they tracked down the murder suspects and arrested them one block south on Paulina.
One man ABC7 talked to on Tuesday night admitted he knows Gaston but would not say if he's related.
"At this time, we don't have anything to say...just trying to get through this like everybody else," the man said.
On Tuesday night, Weis asked for a moment of silence at a graduation ceremony for high school seniors in the Chicago Police and Firefighter Training Academy Program.
Police say Gaston and Walker are both convicted felons. In fact, Gaston has been arrested at least 13 times on charges including robbery and assault.
Valadez leaves behind a pregnant girlfriend who is also a Chicago police officer.
According to the Federation of Police, Officer Valadez's visitation will be on Friday from 3 p.m. to 9 p.m. at Blake and Lamb Funeral Home at 4727 W. 103rd Street. A Catholic funeral Mass will take place Saturday at 10 a.m. at St. Bede the Venerable at 8200 S. Kostner in Chicago. The interment will be private.
Fellow officers mourn Valadez
At the 7th District - one of the toughest in the city - his sergeant and co-workers say Valadez was the right person for his six-man tactical team.
"He was just a great officer. He had had a great rapport with citizens. He was aggressive to the fact that he was good. But he always maintained a level of professionalism," said Sgt. Shannon Jasica, Valadez's supervisor.
"He was a great guy, highly motivated, high spirited, full of integrity," said Melvin Oliver, co-worker.
"He was a great young police officer with a bright future gunned down while basically helping the people of the city of Chicago," said Chicago Mayor Richard Daley.
No one knows the pain the Valadez family is going through more than Donna Marquez. Her brother, Donald, was killed in the line of duty.
"A lot of crying yesterday, a lot of memories, a lot of pain seeing another family go through this, unbearable pain. There's no words that can help this family, just prayer," said Donna Marquez, president, Gold Star Families.
Valadez had only been working for the police department for the past three years. He began in the 22nd District but wanted to move to the 7th District because it was busier and more challenging.
Valadez comes from a police family. His brother and sister are police officers as well as his girlfriend, who was pregnant. And friends said he was very much looking forward to being a father.
The department issued the following statement Monday afternoon: "We would like to express thanks to all the surgeons and medical staff at Stroger Hospital who worked tirelessly to assist Officer Valadez.
"We would also like to express our sincere gratitude to all of Officer Valadez's fellow officers for their tremendous outpouring of support during this very challenging time.
"Our deepest condolences are with the Valadez family; we ask that you keep Officer Valadez and his family in your thoughts and prayers."