Emilio provided ([BBR] p.5) this description of Shaw:

Francis G. Shaw himself took the formal proffer to his son, then in Virginia. After due deliberation, Captain Shaw, on February 6, telegraphed his acceptance.

Robert Gould Shaw …was born Oct. 10, 1837, in Boston, was carefully educated at home and abroad in his earlier years, and admitted to Harvard College in August, 1856, but discontinued his course there in his third year. After a short business career, on April 19, 1861, he marched with his regiment, the Seventh New York National Guard, to the relief of Washington. He applied for and received a commission as second lieutenant in the Second Massachusetts Infantry; and after serving with his company and on the staff of Gen. George H. Gordon, he was promoted to a captaincy.