Pacquiao floored the 38-year-old Kelley at the end of round three, but the jaded American warrior was fortunate enough at that moment as he was saved by the bell.
Sensing victory, Pacquiao quickly went for the kill by sneaking in a powerful left hook to the body that flattened Kelley once again, prompting referee Steve Willis to wave off the bout at the 1:24 mark of the fourth round.
Bobby's townmates here in this bustling city famed as the "Tuna Capital of the Philippines" burst into frenzied celebration upon learning the impressive victory of their hometown hero.
"Siyempre, lipay kaayo mi kay garbo gud na namo ang mga Pacquiao kay taga diri gud na sila. (Of course, we're very happy because the Pacquiaos are our pride here)," said Noy Berto, a tricycle driver.
It was Bobby's 27th win - his 12th via stoppage - in 41 pro fights that include 11 losses and three draws. Kelley fell to 58-7-2 with 39KOs.
In notching his fourth consecutive victory in the US, Bobby showed that he is a class of his own and possesses a fighting character and dedication distinct from his more popular brother Manny.
In his US debut, Bobby defeated Mexican Oscar Villa via a lopsided eight-round shutout November 12, 2004 in Quiet Cannon, Montebello, Califonia.
Bobby then brutally punished Mexican Carlos Navarro on the way to a stunning seventh round KO triumph that earned him the WBC Continetal Americas 130-pound belt on June 17 last year at Table Mountain Casino in Friant, California.
Bobby followed it up with a stunning upset win by split decision over the heavily-favored Carlos "Famoso" Hernandez of El Salvador on October 8, 2005 at Thomas & Mack Center in Las Vegas.
Bobby somehow erased the string of his controversial beating Hernandez with his methotidal demolition of Kevin Kelley, who once reigned as the WBC and WBU featherweight champion when he was still at the peak of his career.