Residents in the neighborhood and family members are shocked and do not understand how this could of happened.
"I don't know what goes through a persons mind. I have no idea why this has happened," said Martin Rivera, a neighbor.
"We don't know we are shocked. Everybody is shocked and we do not know why it happened," said a family member.
Police believe that Roy Perez, 28, got into a fight with his mother and then shot her.
"We believe that the suspect who was detained got in some type of an argument with his mother, shot and killed her, then went next door on some type of a shooting rampage and shot his neighbors," said Los Angeles Sheriff's Lt. Daniel Rosenberg.
The suspect then broke into a next door neighbor's house through a window and fatally shot a woman inside, along with her 4-year-old daughter.
He then shot and wounded the neighbor's 14-year-old boy and a 9-year-old girl before leaving the home. The two children were hospitalized in critical condition.
"And I feel for a child that some crazy guy would come into my house and just kill me for no reason at all and kill my child. You know what that is just horrible,"
The mayor of Baldwin Park grew up in the area.
"It is a very quiet, very unique and a family oriented community here. That is what is important to us in Baldwin Par. For this to of occurred here is obviously very bad tragedy. It has effected parents and students in our city," said Baldwin Park Mayor Manuel Lozano.
When authorities arrived on scene they found the suspect standing in his front yard. They searched him and found a handgun.
Some of the neighbors say that the man seemed very strange to them.
"Well every time we leave like, me and my boyfriend, he'll like stalk us. And then like one day like I tried to lose him like because I didn't want you know. Like every time me and my boyfriend leave like he'll leave too. You know like I feel like he wanted to talk to us try to get our attention and like I never wanted to talk to him. I talked to him once and every time he would talk to me it was kind of weird," said Veronica Rojas, a neighbor.
"He was not friendly, at least not to me. He was just a loner," said Thelma Cuellar, a neighbor.
Police are looking into reports that the man does suffer from mental health problems.
"I do not know if he had problems or not. We do not know and I know very little. It was a surprise and a shock," said a family member.
Neighbors that have lived in the area for decades say that this came out of nowhere.
"This is a nice neighborhood, at least around this small little section right here. We would never expect something like this," said Martin Rivera, a neighbor.
Roy Perez is now facing multiple murder charges.
Eyewitness News reporter Carlos Granda John Gregory and contributed to this report.