It's pretty safe to assume he did, and I don't think this is SOAP. Many women disappear without real resolution of the case without ID of the perpetrator and statistically the vast majority are well known to their victims.

Yes, that's why he killed himself.

I agree. What's also silly is how it was revealed as the 4 season's finale, when her death was basically way past and over with.

Yes, that's surely what we're meant to take away. It's a silly plot point though - the only one in SFU that really bothers me. It doesn't lead to
anything
, so why not leave Lisa's death ambiguous rather than go into soap territory?
Ill be waiting, with a gun and a pack of sandwiches.

It's left up to the viewer to interpret their own way, but I see it as Lisa was killed.