suddenly

adv.

[1]	all of a sudden , in a flash/a moment/a split second , all at once , of a sudden , instantly , instantaneously , momentarily , fleetingly , in the twinkling of an eye , in a trice , quickly , abruptly , swiftly , speedily , rapidly
[2]	all of a sudden , abruptly , short , out of the blue , unexpectedly , dead , without warning , on the spur of the moment , hastily , hurriedly , feverishly
[3]	on the spur of the moment