Q:

An interesting,scary and an old riddle

One night I was visiting a friend of mine . I didn't visit him for a long time , though he was a very old friend . We had the following conversation :-

Friend :- I am very happy to see you my friend !!

Me :- Yeah , it's good to see you again !!

Friend :- Will you stay in my home tonight ? You can sleep in the spare bed this night .

Me :- Yeah sure, it's better to stay a night than walking home .

Friend :- Kill some time here then , for I like having company . It's too lonely alone .

Me :- Yes I can understand . Living alone can be tough .

Friend :- You look very tired . You should just get some rest right now .

Me :- Yes I am a bit tired today , had a lot of work .

Friend :- While you're sleeping , make sure the windows are closed . There are so many bugs in the neighbourhood . Goodnight Then !!

Me :- Ok sure , goodnight !!

After closing the windows, I went to sleep in his spare bed . However, after thinking about the conversation I suspected a big problem and immediately left his house and ran away from the door .
What made me do so?
First to answer this will be marked as the accepted answer :)

A:

Presumably you noticed that

 The first word if each of his first four replies form the sentence "I will kill you".
 If you join it with the first phrase of the fifth reply, you get "I will kill you while you're sleeping.".

