Lee Rigby's widow Rebecca left the courtroom in tears as the jury heard statements from members of the public who witnessed the daylight attack near the soldier's barracks on May 22.
Michael Adebolajo, 28, and Michael Adebowale, 22, deny murdering Rigby, attempting to murder a police officer and conspiracy to murder a police officer.
In a statement read out by the prosecutor, witness Amanda Bailey said she saw a car speeding up and hitting the young soldier, leaving him motionless on the ground.
Initially she thought one of the attackers was reaching for a phone to call an ambulance, but he pulled out a knife.
One of them men "was holding the cleaver in his right hand. He was using a lot of force to hack at the young man's neck", London's Old Bailey court heard.
"I was so shocked all I could do was sit there and stare at what was happening, I couldn't believe what was going on," she said.
"The whole incident took about two minutes, but I can't be sure. It felt like a lifetime."
Another witness, Saraj Miah, described how he was threatened with a gun when he tried to talk down one of the attackers -- and said he could not sleep for a fortnight afterwards.
"I thought that the two black men with knives were going to kill him. I told them not to kill him. They did not listen to me," he said in a statement read out in court.
"I was very shocked by the incident," he added. "I could not sleep for two weeks."
Electrician Thomas Seymour, who had been driving past the scene in Woolwich in southeast London, said in a statement that the victim's body was "covered in blood".
He saw one of the attackers stab Rigby with "forceful" actions between the chest and belly button "10 or 20 times", while the other man was "hacking the victim's head".
