I found this on Gateway.com, Just googled ananias and sapphia. Seems the consensus is that God zapped them. I also understood the text to mean that God killed them.
"As Ananias listens to this expose (NIV's when Ananias heard this does not do justice to the simultaneous action indicated by the present participle), suddenly he falls down and dies (exepsyxen, used primarily in accounts of death as a result of divine judgment--Acts 5:10; 12:23; Judg 4:21). God, the knower of all hearts, has assessed Ananias's unrepentant heart and immediately judged him for his sin (contrast Acts 15:8).
Such a punishment, "death at the hands of heaven," was a recognized penalty in Old Testament and Jewish law....
Such discipline certainly has its deterrent value. The hasty, unceremonious burial of Ananias shows the believers recognize that God's judgment has fallen on one who by his embezzlement had violated the transparent unity of the Spirit-filled assembly (see Lev 10:6; Semahot 2:8). The young men (young in age, not office) cover his eyes and wrap his body in a shroud (synesteilan; the word systellontos, referring to a functionary related to burials, has been discovered on an inscription in a synagogue in Beth Shearim--see Safrai 1976:776). Without the traditional rituals of mourning, Ananias is taken outside the city and buried.Beautiful Conspirator (5:7-11)"
PHG