Richard Hilliard, 24, of Charleston, pleaded guilty earlier this month to manslaughter, telling authorities he shot Booker after the man put a gun to Williamson's head.
Clements was a friend of Booker, Cooper said. Detectives Webb and J.D. Koerber were investigating Booker's murder when they spoke to Clements. Webb wrote in the email that he asked Clements if he knew who killed Booker.
"You better find them before I do," Clements responded.
Clements is an associate of Smith, Cooper said, and both were involved with the City Park Gangsters in the late '90s. Cooper said many of the members of that group were released recently from prison and were "back to their old tricks."
Smith was arrested Monday night and charged with wanton endangerment, malicious wounding and being a felon in possession of a firearm. Detectives are actively searching for Clements, who is considered to be armed and dangerous.
"Based on the large number of shots fired, the fact that an innocent bystander was shot and his serious criminal history, it's clear he shows a total disregard for human life," Cooper said. "We hope someone will turn him in before anyone else gets hurt.
"I'm hoping that Mr. Clements will turn himself in. The fact that he's heavily armed is a concern."
Cooper said detectives have a very strong case against Smith and Clements, adding that once Clements was in custody, the public would be safer.
Williamson currently is being held at South Central Regional Jail while Smith is being held at Southwestern Regional Jail.
Anyone with information can contact the Criminal Investigation Division at 304-348-6480. Anonymous tips are welcome.
Contact writer Ashley B. Craig at ashley.cr...@dailymail.com or 304-348-4850.