Brian Griffin dead, saddest day in 'Family Guy' history sparks viral #RIP memes and merchandise on Twitter [PHOTOS]

#RIPBrianGriffin.

This hashtag has been trending on Twitter and other popular social media networks all day. That's because on Sunday evening (Nov. 24), the beloved "Family Guy" dog was killed-off the show (in a very brutal and bloody way):

As Mstars already reported:

UPDATE: 'Family Guy' countdown to 'Brian Griffin's special announcement' a HOAX! Deceased dog will NOT return from the dead as 'Christmas Miracle' around December 6? 

Brian Griffin's death shocks 'Family Guy' viewers, fans protest grisly passing with Facebook petition: Proof that TV dog is dead, not coming back, welcome Tony Sirico as Vinnie

Spoiler alert - ladies pup Brian Griffin DIED on last night's shocking episode of "Family Guy" (Nov. 24). The poor pup (voiced by show creator Seth MacFarlene) was tragically struck by a car and ultimately passed away from his injuries. The beloved TV dog starred on the hit animated sitcom for 11 seasons.

Fox warned viewers that a main character was biting the dust on this weekend's episode - but who would've thought it'd be Brian!

Stewie Griffin was ready to go back in time and prevent the accident, but he'd JUST taken apart his time machine. Therefore, he was unable to save the bloody and bruised Brian:

"Family Guy" executive producer Steve Callaghan tells E! Online, "This was an idea that got pitched in the writers room and it sort of caught fire, and we thought it could be a fun way to shake things up... We started talking about what the next couple episodes could be and we got very excited about the way this change will affect the family dynamics and the characters."

According to Callaghan, killing off a human family member would be "too traumatic," so writers settled on the dog. Fellow cast members Mila Kunis and Seth Green were "surprised" by the news, but "glad it wasn't them."

Several fans were utterly heartbroken by Brian's tragic and sudden demise. These "RIP" Twitpics quickly went viral online:

Now, fans can even own a part of "Family Guy" history with RIP Brian Griffin merchandise offered on Galloree.

T-shirts sell between $12-17 and come in assorted colors:

Want a mug? That'll cost you $15:

Stay tuned as #RIPBrianGriffin continues taking over the web.