Transcript for Video captures firefighter using sign language to communicate with deaf child

Finally tonight here, America strong. The firefighter, the 9-year-old boy and their connection. This is Manchester fire lieutenant Mike Rheault. And 9-year-old Tegan Kerr in Manchester, New Hampshire. The fire department responding to a call when the two spot one another. Instantly, they connect. My name is m-I-k-e. Mike. Reporter: Tegan then signs his name back. He has cerebral palsy and is non-verbal. T-e-e-g-a-n? Nice. One one more, one more. Reporter: Lieutenant Rheault then teaches teegan a new word. Fireman. Fireman. Teegan, that is so cool. Reporter: A high five for teegan. Atta boy! Reporter: His mom capturing the connection. I made me cry after I came back inside, and teegan's just thrilled. Reporter: It turns out both of his parents were death. Sign language was his first language. Tonight, the boy's mother with a message for anyone who sees someone different. Talk to them. Talk to all the kids. If you see a kid at the playground who is different or had special accommodations they use, they just want to be your friend. Reporter: And teegan tonight visiting his new friends at the fire station, smiling in the fire truck, wearing the fire helmet that's now his. I love that smile. Thank you for watching here on a Tuesday night. We'll see you a bit later here for the president's state of the union. I'm David Muir. Good night.

This transcript has been automatically generated and may not be 100% accurate.