TODAY | July 28, 2013
>>> most people don't get too excited when the garbage truck comes to their neighborhood. in central california there's one guy who can't wait for it. now the man who drives that truck has formed a friendship with his biggest friend. miguel almaguer has their story.
>> reporter: 4-year-old grayson and his mom chrissy can hear the rumble. they know he's on the way.
>> he is jumping up and down and flapping his hands and just feeling so much joy.
>> reporter: frank diaz looks forward to this stop all week. like so many little boys , grayson loves the roar of the garbage truck , but he isn't like most boys.
>> what a guy. what a big guy .
>> reporter: grayson is autistic. he struggles to connect, to communicate with his parents.
>> i didn't have a typical child who spoke or said, mommy, i'd like to get out of bed now or mommy, i love you.
>> reporter: a few weeks ago when frank pulled up, grayson broke his silence.
>> he said "i want truck." it was a breakthrough into my world. not only did he talk to me, but he said three words.
>> reporter: for a family living with autism, it was a milestone.
>> it's such a rare but special moment between the two of us. and so it was honestly -- it was magical.
>> reporter: the kellys have two boys, little brother parker who is just 2 shows signs of autism, but is too young to be officially diagnosed. chrissy shares her family's story on her blog, connecting with moms around the world. but it's one man --
>> dear frank.
>> reporter: -- who has made the biggest impact on her son's life.
>> i see a glow on his face, he's excited. it seems like he's connecting. that's the joy i get out of it.
>> frank gives me hope. people out there are good.
>> reporter: frank even carries grayson 's picture in his truck. their connection made with just a few simple words, baugh meaning that goes so much deeper. for "today," miguel almaguer, nbc news, fresno, california.