If you can pull the wire from the previous receptacle/light fixture that would be best but it may be hard to determine which one it is. Also the wire is probably stapled to a stud somewhere alone the way.
Personally I would grab a small junction box with a metal plate cover, mount the box on a stud below the cut off line, pull the exposed wire into the box using the proper connector, cap off the wires with marets and then close off the box. Not sure if that is legal with code but it would be safe.
Box
http://www.homedepot.ca/product/util...-7-8-in/977520
Cover
http://www.homedepot.ca/product/util...k-cover/977524
Connector
http://www.homedepot.ca/product/3-8-...-of-125/910047
Marets, one for hot, one for neutral, one for ground, hook ground up to junction box also.
http://www.homedepot.ca/product/marr...ck-of-3/907010