Brandon Karr and Rojelio Heredia, who are being held without bail, are facing several charges, including first-degree murder and attempted first-degree murder.
Dear has been undergoing treatment at the state mental hospital since Martinez deemed him incompetent in May.
Judge Stephen Collins sentenced Abrams to 20 years in prison on Aug. 3.
Authorities say Long was arrested on suspicion of first-degree assault and a related weapons charge. Keith County Jail records say he remained in custody Tuesday morning.
The shootings happened at the Berkeley Village Mobile Home Park, near Arvada.
There is no word on the extent of their injuries yet, nor any description of a suspect or suspects.
Investigators are asking anyone with information about the shooting to call Detective Mike Prince at 303-739-6127. Tipsters can also report information to anonymously to Metro Denver Crime Stoppers by calling 720-913-7867 and may be eligible for a $2,000 reward.
Martin is being held without bond at the Arapahoe County Jail.