The standoff began Sunday shortly before 3 p.m. when Lopez barricaded himself in the attic of a house on West Belmont Street at Vine Avenue and began firing a handgun.
The Ontario Police Department's SWAT team responded to the scene. Authorities evacuated several neighbors and cordoned off the neighborhood for several hours as the SWAT team attempted to make contact with Lopez.
SWAT officers entered the home just before 1 a.m. Monday to find Lopez dead of a self-inflicted gunshot wound.
No one else was injured in the incident.