Phoenix fire officials said Eric's injuries left him without a heartbeat and he was not breathing when firefighters arrived on the scene.
Medical personnel were able to revive Mendez and rush him to Phoenix Children’s Hospital.
The now 14-year-old boy survived all of his injuries and thanked first responders and nurses for all of their life-saving efforts on Wednesday morning.
"They save me and they save other people too," Mendez said. "I'm happy to be alive."
"I almost lost my grandson, but every day I remember how important he is to our life," Eric's grandmother Margaret Chavez said.
Retired Phoenix Fire Capt. Brian Mangis said Eric was in full trauma code when they arrived at the house.
"It is not breathing and no pulse, but this time we knew he needed a surgeon," Mangis said. "We decided at that point to just get him in the ambulance and do all the treatment there."
Mangis said it took 18 minutes to respond to the house and get Eric to the hospital. To save the boy's life, a trauma surgeon cut open his chest and sewed his heart back together in the emergency room.
"He's made such an incredible recovery," said Phoenix Children's Hospital surgeon Lisa McMahon. "He has a supportive family, and it's nice to see him going to school and walking around and talking with us."