Muhammad, 48, was pronounced dead at 9:11 p.m., said Larry Traylor, spokesman for the Virginia Department of Corrections, speaking in a steady drizzle outside the Greensville Correctional Center.
Asked for last words, Muhammad, wearing a blue shirt and denim jeans, declined to speak and "did not acknowledge us," Traylor said. The execution took place without incident, he said, with Muhammad displaying no emotion.
Issuing a statement on behalf of Muhammad's family and lawyers, attorney Jonathan Sheldon said they "deeply sympathize with the families and loved ones" of the victims, and offered "prayers for a better future" for those left behind.
Virginia Gov. Tim Kaine denied Muhammad's appeal for clemency earlier in the day, and the Supreme Court on Monday rejected his bid to halt the execution. His lawyers said he was mentally ill, an argument that had failed previously on appeal.
So many relatives of Muhammad's victims were on hand for the execution, Traylor said, that the prison could not accommodate all those who wished to see the Army veteran draw his last breath.
Sonia Wills, mother of one of the victims, Montgomery County bus driver Conrad Johnson, came from Dallas to be on the prison grounds, though she did not want to witness the execution.
"He needs to be gone from this Earth," Wills said. "That man has caused too much disturbance in everyone's life." She said she would "breathe a sigh of relief" when Muhammad died.
Muhammad "staggered" into the death chamber shortly before 9 p.m., assisted by corrections officers, said Jon Burkett, a television reporter with WTVR in Richmond and one of four media witnesses selected to view the execution. He did not appear sedated, Burkett said.
In addition to denim clothing, he wore shoes resembling flip-flops, and he was clean-shaven.
"He looked calm," Burkett said.
Traylor said Muhammad looked around the room with some curiosity and did not resist as corrections officers strapped him down.
A curtain between the chamber and viewing room was closed while an intravenous line was inserted. After the curtain was reopened at 9:06 p.m., Muhammad did not acknowledge prison observers when asked for his last words, according to witnesses. He closed his eyes and turned his head to the right.
At 9:07 p.m., as a mixture of three chemicals flowed into his veins, Muhammad began to twitch and blink, and breathed deeply seven times. He was "motionless" by 9:08 p.m., Burkett said. Medical personnel pronounced him dead three minutes later.
As his execution drew near, Muhammad "accepted his fate," said one of his lawyers, J. Wyndal Gordon, who met with Muhammad earlier in the day. "He has no remorse because he maintains his innocence," Gordon said, adding that Muhammad stated that "prison did not make him, so prison will not break him."
During the day, Muhammad was allowed to meet with members of his family, including a 27-year-old son, Lindbergh Williams.
For his last meal Muhammad ate chicken with red sauce and chocolate cake, Gordon said.
Muhammad's family said they will hold a news conference at noon today in Richmond.