Easy-peasy!
That would be the story "Bobby", which you may have seen in one of two versions. It was originally part of a Dan Curtis made for TV anthology movie named DEAD OF NIGHT from 1977, which is the much less famous twin to the famous TRILOGY OF TERROR (1975). Both TRILOGY (famous for the segment "Amelia" - an adaptation of Matheson's story "Prey" - and its Zuni fetish doll) and DEAD OF NIGHT are compendiums of Richard Matheson stories and the ending of "Bobby" is certainly ultra-creepy and caused me many a chill back in the day (as the kids say).
Later, some opportunist (well, Dan Curtis himself, no doubt) made TRILOGY OF TERROR II (1996) which was straight to video and showed a lot on sci-fi channel. It had "He Who Kills", which is purportedly a sequel to "Prey"/"Amelia" but is really pretty much just the same story rewritten in a new setting, "The Graveyard Rats", which is a famous Henry Kuttner story from the WEIRD TALES pulp days and, yes, a remake of "Bobby" (less effective, IIRC). You're more likely to have seen this version if you saw it recently.
To make sure that the dumbing down/lowest common denominator-ization of all pop culture continues unabated, the producers of the DVD version of the original, 1977, DEAD OF NIGHT have plastered the "reveal" image of Bobby on the cover, so that the payoff is ruined (see also, recent trailer for QUARANTINE) and so that not a drop of potential money is wasted ("we gotta get the money shot on the packaging" said the fat man, hacking around his smelly cigar and wiping his greasy hands on his silk suit) - all while also assuring that any potential renters of said film will be disappointed that the movie wasn't what it semed and the ending was ruined for them and then they can blame the film and never rent anything from 1977 again. And so the training of the populace that everything old is bad and that memory and history are to be avoided at all costs (the better to sell you the same thing over and over) continues apace....
But, yes, track it down by all means. "A Second Chance" is weak tea (an attempt to sell the anthology as a series, and prove they could do lighter, "weird" tales and not just horror, I presume) but "No Such Thing As A Vampire" is still good fun (especially if you'ver never read the story) and "Bobby" is pretty damn great.