New York (CNN) -- An apparent dispute over housing ended with an 86-year-old New York man shooting his grandson and killing his grandson's girlfriend before fatally shooting himself, a law enforcement source said Saturday.
Police were still trying to sort out what led Heriberto Pagan to drive from his home in Brooklyn to his daughter's Staten Island house Friday and shoot two people before taking his own life.
A law enforcement source said investigators were looking into the possibility that the grandson "was trying to take over" the home with his girlfriend and Pagan "wasn't appreciative of the way" his daughter was being treated in the process. It was not clear whether the daughter was at home at the time.
Police found Pagan, a gunshot wound to the head, outside his car Friday evening near the home where the shootings occurred. He was hospitalized in critical condition, but died Saturday morning, police said.
In the vicinity, police were alerted to another shooting victim, Pagan's 47-year-old grandson, who was critically injured with a gunshot wound to the head and found outside the Staten Island house where he lived with his mother and girlfriend. The grandson has not been identified.
Inside the house, police found a second victim, Claritle Christina Huerta, 28, also shot in the head. She was pronounced dead at a local hospital.
"This is like a nightmare," neighbor John Rina told CNN affiliate WCBS.
Police said Pagan shot his grandson as the younger man approached the house. He then shot Huerta inside before driving a few blocks and shooting himself, authorities said.
"I just heard a man screaming 'help me, help me,'" a neighbor, not identified, told WCBS.
A 4-month-old boy was found unharmed in the home and placed in the care of child welfare authorities, police said.
"There [were] a lot of problems in that house, I could say, but it never really exploded the way it [did] today," an unidentified neighbor told CNN affiliate NY1 News. "This is actually probably a buildup to everything that's been happening for ... years."