Also killed in the Saturday shooting were Moore's father, Bruce Moore, 66; her husband, Michael Moore, 42, who used his wife's last name; and her son, Shannon Moore, 17.
While Guzzo's motive died with him, neighbors and family members of the victims pointed to his growing annoyance with noise from neighborhood dogs.
"He hated them. But everyone here has dogs," said Joni Flood, 27, who lives a few doors down from the victims.
Libni Deleon, 26, said he returned home from work just a few months ago to find Guzzo standing by his back gate, where Deleon's two dogs were on the patio barking.
"He said, 'Your dogs are barking. I'm here to live in peace,'" Deleon recalled.
Moments after Saturday's killings, Guzzo went back to Deleon's home and began kicking on the front door.
Deleon's wife, Vanessa, had just gotten out of the shower. She grabbed their two children and ran upstairs to hide in the bathtub.
Libni Deleon went toward the door as Guzzo blasted two holes through it, sending about 20 shotgun pellets into the walls at the back of their home.
He ran upstairs to get his gun, opened the window and began to yell at Guzzo, who opened fire again before walking back to his own home to kill himself.
"I feel pretty darn lucky," Libni Deleon said.
The victims' family members, meanwhile, are struggling to come to grips with their loss, dumbfounded by the sheer senselessness of the killings.
Standing amid pools of drying blood on the home's back patio where the two men were apparently shot first, Michael Moore's brother called the killings "angering beyond belief."
"It just angers me looking at all this because I just feel for my brother," said Patrick Riley, 41. "The helplessness."
The patio wall was chipped with pockmarks from the shotgun's blast. Police haven't given specific details of the attack, but Riley said he thinks Guzzo shot his brother over a 6-foot cinderblock fence while he worked on an engine.