Guillermo has worked in violence intervention and prevention, plus youth development and civic engagement for over 20 years. He began as a City Year member in 1994, working in North Lawndale. He is a Public Allies AmeriCorps alumnus and has worked internationally and nationwide with CeaseFire/Cure Violence. At BUILD, Inc., Guillermo developed a tiered leadership development ladder for youth at risk of violence and gang involvement. He also established the BUILD youth council and annual youth-led gang conference, institutionalizing youth leadership within that organization. Guillermo has volunteered with FDLA since its inception and recently completed a term on the board of directors.