Ludlow said Petersen intended to kill Ryker then turn the gun on himself, but he was stopped by a family member. During a very brief news conference Friday evening, Ludlow added that the motive for the killing was still under investigation.
Petersen and the boy live at the home, Ludlow said, though police did not provide additional details about other occupants of the home.
Posts on Petersen's Facebook account include many pictures of his young son. Petersen also posted multiple comments that indicated he had been having a "bad day" but that being with his son made it better. Conversely, some posts indicated that his mood also was affected negatively when he wasn't with Ryker.
"Not cool, I don't have my son," reads one post from Feb. 27.
A family member and a friend of Petersen's who were contacted on Friday declined to comment.
But neighbor Fran Keller, who lives several blocks away, described the residents of the home as an elderly couple with grandchildren. Keller was out on a walk when she saw police and learned of a shooting.
"I'm pretty upset," she said. "How do you go on and even live after this?"
Across the street, Donnett Beamsderfer was dozing off while watching crime shows early Friday afternoon. She said she heard people yelling and thought it was just part of the TV show. Then about 1 p.m. she heard what sounded like a gunshot.
"I thought, 'Wow, that was really loud,' " she said.
A friend later called Beamsderfer after learning about the shooting on the news. When she heard what happened, Beamsderfer realized the yelling and gunshot she heard wasn't part of the TV show.
Beamsderfer, who moved into the neighborhood last year, said the area is generally quiet and doesn't have much crime. Like several other neighbors, Beamsderfer said the residents of the home where the shooting happened generally kept to themselves.