Philadeliphia Police caught up with McGillvary at the Greyhound bus terminal after an "overwhelming response and dedicated effort by the public and law enforcement" helped track him down, Union County (N.J.) Prosecutor Theodore Romankow said in a statement.
The "homefree" hitchhiker came to the attention of police after Joseph Galfy, 73, was found dead in his Clark, N.J., home on Monday when officers responded to a call for a welfare check, Romankow said.
An autopsy revealed Galfy died on Sunday of blunt force trauma to the head.
McGillvary burst onto the viral scene in Fresno, Calif., in February when he helped save the life of a stranger and distract his assailant until police could arrive.
Known only as Kai at the time, McGillvary's colorful interview with local Fox affiliate KMPH turned him into a YouTube sensation.
McGillvary will be held at Union County Jail in Elizabeth, N.J., on $3 million bail.