After his two years of study with Gazzam, Peck entered Rush Medical College, Chicago, Illinois, in autumn 1846, and graduated in 1847.
During the summer after graduation, Peck toured the state of Ohio with William Lloyd Garrison and Frederick Douglass.
At the suggestion of Martin R. Delany, Peck moved to San Juan del Norte, Nicaragua, in early 1852.
Peck was killed in spring 1855 in a skirmish between Democratic forces and their Republican rivals at Jalteva, Nicaragua (near Granada) in the Filibuster War.
Peck's death is recollected by Charles William Doubleday (1829–1909) in Chapter 4 of his Reminiscences of the 'Filibuster' War in Nicaragua.