Not true. Randy Weaver's friend (can't recall his name) was with Randy's son and dog investigating why the dog was barking. The agent was in full camo in a fixed position on the ground. As the dog, out front, approached the agent's position of concealment the agent shot it. Randy's son returned fire in the direction that the shot came from hitting the agent and was fired on and hit in return.
The family friend didn't see the agent and the Weaver boy probably didn't see him either. At least not clearly. The friend carried the boy back to the house which was then put under seige. It was sometime later that Horiuchi took his famous shot. He was shooting at the friend who was running from an outbuilding where the boy's body lay while Sandy Weaver held the door open. He hit Sandy and her baby that she was holding in her arms.
That was the account I read in The American Hunter, an NRA publication, FWIW.
The shooting of the mother with the baby in her arms was an intentional act. The government sniper drew what he saw before he fired his shot at her, it was a woman holding a baby.
The rules were changed by the feds before going after Weaver. What happened was really just a government hit team intentionally killing a mom.
That came out at trial, about the drawing made by the government sniper showing the mom behind a screen type door.
It was no accident whatsoever, a deliberate shot made at an unarmed woman looking out towards whatever unknown evil men were killing her dog, her son and shooting at them.
The local prosocutor should have tried the entire lot, and the government sniper should have gotten the death penalty.