With these specific instructions, I was ordered to rejoin my company; and Lieutenant Beauregard was directed to take general charge of the movements of Smith's brigade. When Beauregard and I reached the top of the second ridge we found we were 50 yards, or less, in rear of the Mexican detachment, which was facing Riley. All was quiet. In a very few moments Riley's fire commenced.
The engineer company, followed by the rifle regiment was then forming in line, under cover, in rear of the Mexican detachment, whose attention was concentrated on Riley, in their front. We were between that detachment and the Mexican works. A small portion only of the Rifle Regiment was in line, when the firing with Riley became very severe, and the order was given for the engineer company and rifles to rise and fire into the backs of the enemy. That fire was very destructive. The Mexicans were astounded; faced squarely about, and in a moment precipitately retreated.
In my official report it is stated that: "Colonel Riley's advance became engaged with a very strong picket, some 300 yards or more from the rear of the [enemy's] battery, near the crest of the ridge; the engineers and rifles came up at once in position to take the picket in rear, delivered a deadly volley within 50 yards, cheered and rushed on. The enemy's force fled; the head of our column crossed the line of their retreat, which brought the right of the column [engineer company and rifles] conducted by Lieutenant Beauregard, in contact with the Seventh Infantry, which formed the left of Colonel Riley's brigade. I went into the enemy's battery with the colors of the Seventh Infantry, my company immediately behind me. The enemy, or at least a portion of them, stood to their guns well, and delivered a fire of grape into our troops when the head of the column was within 25 yards of their pieces. Our troops followed the retreating enemy without halting until they were beyond the reach of our musketry. Lieutenant Beauregard then strongly advised that the troops be halted and formed. A short time afterwards General Twiggs, came up. The pursuit was resumed. At San Angel we had an unimportant skirmish". (Ex. Doc. No. 1, Appendix, p. 68).