70s-80s horror movie with four aliens of different types attacking a small town,...

I'm trying to identify a horror movie. Summary:

• English-language movie set in rural America. Saw it in the 80s, but it could be a 70s movie. Had a B-movie vibe to it.
• An alien spaceship crashes in the woods next to a small town. The aliens start attacking the townspeople. As always, the local police are useless. A mysterious out-of-towner comes to the rescue.
• The first alien is an insectoid type. Its hard exoskeleton is impervious to bullets. The hero kills it with sonic waves.
• The second alien is a Bigfoot-type monster. Not entirely sure how this guy was killed, but I vaguely remember that it involved getting shot with a shotgun of some sort.
• The third alien is a reptilian who created mirror images of himself so the hero couldn't kill him. Eventually, the hero finds his hiding place and kills him.
• The final twist is that the hero himself is one of the aliens and shows his real form to one of the townspeople. A policeman walks in, misunderstands, and shoots the hero, killing him.

You're looking for the 1976 B-movie The Alien Factor. From an online synopsis:

It's set in a small American town and opens with a stereotypical sci-fi/horror movie scene: a young couple are drinking and making out in a parked car in the middle of nowhere and are suddenly attacked by a monster which kills one of them and leaves the other in shock. Turns out an alien spacecraft has crashed nearby, freeing the three ferocious zoological specimens that were on board. Now said beasts are roaming the countryside, killing random rubes. The local police (all two of them) are stumped until a mysterious expert arrives in town to investigate a supposed meteor crash, and ends up helping hunt down and dispose of the alien monsters.

The 3 aliens are a giant insect-looking thing, a big hairy creature and a reptile which uses holograms. And the mysterious 'expert' turns out to be an alien in the end. Here's the trailer: