They are effective against unarmed and under armed people.   The guy that got killed only had a bat someone properly trained in how to use a taser should have no problems in neutralizing a person with a bad with a taser.  Also a person properly trained in using a gun should have no problem in neutralizing a person with a bat without killing them. 

There was more than one officer in the scene.

Yeah it's America where you have to assume that everybody has a gun. The police having heavy weaponry is a side effect of the fact that people can go out and buy all kinds of guns. What's a teaser going to do to people with guns?
Note that I'm not giving any excuse as to the shooting of these two people.

Ms. Jones’s boyfriend, who asked not to be named, said that he had been present when the shooting occurred, and that Ms. Jones had gotten up from bed to open a front door — shared by the first and second floors — for arriving police officers. He said Mr. LeGrier’s father, who is also the landlord for the building, had telephoned Ms. Jones from the second floor to alert her that the police were on their way and needed to be let in

He said that when the officers arrived, Mr. LeGrier seemed to have rushed to the bottom of the stairs with his bat at nearly the same time Ms. Jones was opening the door.

“Then the shooting just started coming — bam, bam, bam!” he said.

I don't know the exact circumstances of the incident but I do know someone rushing me with a baseball bat at 4:25 am would freak me the hell out and I would not hesitate to shoot to kill if I had a gun at my disposal.

Still, I'd like to learn more information.

I was wondering the same thing but police are trained to shot the torso since it's the easiest body part to hit and it helps prevent the possibility of hitting someone nearby in case of a miss.

Here's a link for more info: https://answers.yahoo.com/question/index?qid=20080910204651AAlEeaG

Only in films is shooting to disable a thing in real life aim at centre of mass. 

Maybe Police are always ready to shoot because of incidents like below (NSFW)

https://www.youtube.com/watch?v=r893R7mwqwo

https://www.youtube.com/watch?v=LuOEJKiKELA

https://www.youtube.com/watch?v=60a2xIz600A

This shit's scary. I would have opened fire sooner on that third one.

Or the people are fucked up in US or the US police...

That's some fucked up shit right there. Second video is scary as fuck.

That's what happens when the law allows you to keep and sell firearms in many parts of the country. In all the other countries mentioned people are surprised if a civilian pops out a firearm, in the U.S. police are pretty much expecting it.

I get that US police is more trigger happy than police forces in countrys with tighter gun laws. I know I would be on my fucking guard if I knew basically everyone could whip out a gun on me.

However, a lot of US law enforment also seems to be underqualified and badly trained for the job.
In the US, as far as i'm aware, the training varies by state, but can be as short as only six weeks of police academy, with 19 to 21 weeks being more commom (training is in most cases continued for 6 to 12 months on the job). A highschool degree is required to be able to apply.

To contrast, in my country, the minimum training required is 30 months for the basic training and 36 months for a university degree in police work (usually required for higher police positions). New officers are then trained on the job for up to two years after that. This amounts to 4,5 -5 years of training compared to the ca 1,5 the average US cop gets. A high-school degree as well as passing an entrance exam (comprised of an IQ test, medical evaluation, psycological evaluation and a fitness test) is required to start training.

I feel like, a cop with sufficient training should be able to disarm a guy with a baseball bat without making use of his firearm. (I'm not talking about "shooting a leg" btw. I know cops are trained to go for the mass of the body)