An attempt by police to prevent a revenge gang killing was behind Monday's Humboldt Park shootout, in which two gang members were killed, Police Supt. Philip Cline said Thursday.

Tristan Scaggs, who was wounded in the shootings, was ordered held without bond after being charged with two counts of murder and conspiracy to commit murder. A police officer also was wounded in the firefight.

Scaggs, 19, was not present at his bond hearing Thursday at Cook County Criminal Court. He is listed in guarded condition at Mount Sinai Hospital from a gunshot wound to his left shoulder, Cook County Assistant State's Attorney Ursula Walowski said.

Scaggs, of the 1200 block of South Homan Avenue, is also charged with two counts of attempted murder and five counts of aggravated assault of a police officer, police said.

Lamel Burns and Melvin Martin also have been charged with felony murder attempted murder and conspiracy to commit murder in connection with their alleged involvement in the murder plot, police said.

Chicago Police Supt. Phil Cline called the murder plot "calculated," adding that the suspects "used masks and latex gloves to hide their identity and thwart any evidence of fingerprints and gunshot residue."

The Chicago Police Special Gang Task Force had been monitoring gang members' cell phone conversations and learned of a suspected murder plot that was about to unfold in the vicinity of Pulaski Road and Iowa Street, prosecutors said.

Prosecutors said Scaggs, William Tyler, 23, and Marcus Thomas, 21, were driving in a stolen car, allegedly on their way to kill a rival gang member after being directed by look-outs who spotted the man.

Police officers tailing the car intervened, stopping the car at the intersection of Augusta Boulevard and Kedzie Avenue, prosecutors said.

The police officers approached the car and noticed that Thomas, sitting in the backseat, was holding an AK-47, prosecutors said.

Tyler was the driver of the car and Scaggs was in the front passenger seat, holding a 9 mm pistol, prosecutors said.

Prosecutors said that when the officers saw the gun, they drew their guns and a firefight ensued, leaving Thomas and Tyler dead and Scaggs and one of the police officers wounded.

The wounded police officer had been shot in the finger and is out of the hospital, police said.

Scaggs is charged with two counts of felony murder because Tyler and Thomas were killed while they were in the act of perpetrating a felony, according to a spokesman for the Cook County State's Attorney's office.

According to police, the gang also used the Illinois Department of Corrections Web site to get pictures of the individual targeted by the hit.

Police said the planned attack was in retaliation for the slaying of Marquel Harper on Friday, who was gunned down while walking a child to school. Police attribute 19 murders since January to the mounting tensions between the feuding Traveling Vice Lords and New Breed gangs.