He acquired the rank of captain in the Philippine Revolutionary Army.

His defection was likely a reaction to racist treatment of African-American soldiers within the United States armed forces at the time, as well as racist sentiments expressed towards the Filipino resistance, who were frequently referred to by American soldiers as "niggers" and "gugus".

[6] After two other black deserters were captured and executed, President Theodore Roosevelt announced he would stop executing captured deserters.

A substantial reward was offered for Fagen, who was considered a traitor.

There are two conflicting versions of his fate: one is that his was the partially decomposed head for which the reward was claimed, and the other is that he married a local woman and lived peacefully in the mountains.