It is also rather odd to say "The old lady died because the robber strangled her". We don't usually say someone died "because" of anything. People die "from/of" a disease/gunshot or "due to" something. In this context, I would probably use something like "The poor lady was killed by a robber who strangled her" or "The robber strangled the poor lady [to death]". Some people will say that "to death" is redundant because usually strangulation results in death. However, it can mean to cut off the oxygen supply temporarily by pressing on the windpipe.
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