Edmonson said police video shows Vincent, a 13-year veteran of the state police, offering assistance to the apparently stranded man.
The video then shows the pickup truck door opening and Daigle coming out with a shotgun. Edmonson said the tape shows the shotgun blast.
After the shooting, Edmonson said, Daigle wandered into the road and walked over to Vincent, asking him if he was alive. Edmonson said the gunman tells Vincent: "You're lucky — you're going to die soon.'"
That's when two or three drivers stopped, one of them spinning around on the two-lane highway. That driver wrestled the shotgun away from Daigle, Edmonson said. With the help of the others, he got Daigle to the ground and snapped Vincent's handcuffs on his wrists.
At a news conference on Monday, Edmonson applauded the civilians who rushed to the trooper's aid, singling out the motorist who grabbed the gun.
