In June of 1807 General Senarmont was the artillery chief of Victor's I Corps and at Friedland on 14 June demonstrated what aggressively handled artillery, maneuvered to close with the enemy, could do.
The French main attack was assigned to Ney and the VI Corps and Ney's first attack was defeated and thrown back. After Senarmont began his attack, which then became the French main effort by default, Ney reorganized his corps and attacked a second time, and was successful.
Dupont advanced in his own if I'm not mistaken and was supported by some of the corps artillery under Captain Ricci. Then Senarmont asked Victor for permission to take control of the entire I Corps artillery, which was given, and then he proceeded to first support Dupont, and then to advance past Dupont and attack the Russian center and then destroy it.
No one gave Senarmont an order to do what he did. It was done on his own initiative and with Victor's permission. It wasn't either Victor's idea or his order to proceed.
The Russian center at Friedland was not retreating once the battle began. Orders had been given to withdraw, but they had to be canceled when Napoleon showed up with the main army. Dupont's advance against the Russian center shifted to supporting Senarmont's attack on the Russian center which he destroyed with artillery fire. Senarmont began by supporting Dupont's advance and then saw an opportunity for decisive action against the Russian center and attacked it by a rapid advance of 30 artillery pieces, supported by 6 more in reserve.
The idea that the Russians were retreating after the attack began is incorrect. You can find the I Corps (to which Senarmont was Victor's artillery chief) after action report in La Sabretache. Senarmont's after action report can be found in Grands Artilleurs by Maurice Girod de l'Ain which not only covers Senarmont, but also Eble and Drouot. Yermelov also describes the destruction done by Senarmont's large battery and it can also be found in Boulart's memoirs as he was an eyewitness to the action.
Senarmont wrote to his brother of the artillery action on 14 June in a letter on 26 June: 'The position of the enemy showed 4,000 dead on this spot alone. I lost my chief of staff, Colonel Forno, killed by a ball at the end of the action. I have had three officers and sixty-two gunners hors de combat, and a charming horse wounded under me; I fear I shall not be able to save him.’